docs: update docs for build updates

diff --git a/README.md b/README.md
index af1878a..283e8f3 100644
--- a/README.md
+++ b/README.md
@@ -1,19 +1,21 @@
-# Jade Firmware
+# Jade Firmware Development
 
-NOTE: The below instructions are for Jade developers with access to Jade development boards or for those wanting to build and flash their own esp32/esp32s3 consumer devices - e.g. M5Stack or TTGO T-Display boards.
-They are not for updating the firmware of an official Blockstream Jade HW unit - these can only be updated in-app, or using the 'update_jade_fw.py' script - see FWUPDATE.md
+* DO NOT ATTEMPT TO BUILD/FLASH WITH OFFICIAL BLOCKSTREAM JADE HARDWARE UNITS
 
-* DO NOT ATTEMPT THE BELOW WITH BLOCKSTREAM OFFICIAL BLOCKSTREAM JADE HW UNITS
+The below instructions are for developers with access to Jade development
+devices, or for those wanting to build and flash their own esp32/esp32s3
+DIY consumer devices such as M5Stack or TTGO T-Display boards.
 
-To build you can use the docker image (see Dockerfile) or install the esp-idf toolchain and repository following the commands below.
+Official Blockstream Jade hardware units can only be updated via a supported
+companion app, or by using the [Firmware Update Instructions](./FWUPDATE.md).
 
 # DIY Hardware & Programming Notes
-For information about suitable DIY hardware, as well as suggested configuration profiles and notes on secure boot,
-see [DIY Guide](./diy/)
+For information about suitable DIY hardware, as well as suggested configuration
+profiles and notes on secure boot, see the [DIY Guide](./diy/)
 
 # Build dependencies
 
-Cmake and ninja are needed to build the firmware.
+Cmake and ninja are needed to build Jade firmware images.
 
 On Debian based distributions, install with with:
 
@@ -27,39 +29,25 @@ On MacOS:
 brew install cmake ninja
 ```
 
-Make sure to use a recent Python version (e.g. Python 3.11) as the current system version which is used by the install script below.
-Failure to do so may result in problems installing Python dependencies.
+Make sure to use a recent Python version (Python 3.11+) when running the
+commands below. Failure to do so may result in problems installing Python
+dependencies.
 
-# Set up the environment
+# Set up the build environment
 
-Jade requires the esp-idf sdk.
+Jade requires the esp-idf SDK. You can use our docker image to build or
+install the esp-idf toolchain locally using the commands below.
 
-More information is available in the [Espressif official guide](https://docs.espressif.com/projects/esp-idf/en/v5.4/esp32/get-started/index.html).
+See the [Espressif official guide](https://docs.espressif.com/projects/esp-idf/en/v5.4/esp32/get-started/index.html)
+for more information on the available tooling.
 
-Get the esp-idf sdk and required tools:
+# Device targets
 
-```
-mkdir ~/esp
-cd ~/esp
-git clone -b v5.4 --recursive https://github.com/espressif/esp-idf.git
-cd esp-idf
-git checkout 67c1de1eebe095d554d281952fde63c16ee2dca0
-./install.sh --enable-gdbgui esp32 esp32s3
-python ./tools/idf_tools.py install qemu-xtensa
-```
-
-Set up the idf environmental and make the `idf.py` command available:
-
-```
-. $HOME/esp/esp-idf/export.sh
-```
-
-# Devices
-
-There are currently three Jade device targets:
+There are currently four official Jade device targets:
 - jade: The original Jade 1.0 with a selection wheel.
-- jade_v1_1: Jade 1.1, which has a rocker/jog-wheel in place of the selection wheel.
-- jade_v2: Jade Plus, with a larger screen and left/right selection buttons in place of a wheel or rocker.
+- jade_v1_1: Jade 1.1, with a rocker/jog-wheel instead of the selection wheel.
+- jade_v2: Jade Plus, with a larger screen and left/right selection buttons
+  instead of a wheel or rocker.
 - jade_v2c: Jade Core, Jade Plus without camera and battery.
 
 Change `jade` in any calls to the `switch_to.sh` script below to the
@@ -67,18 +55,21 @@ appropriate device you wish to target from the list above.
 
 # Serial port
 
-The serial port pseudo-tty file for Jade access via USB is usually `/dev/ttyACM0` or `/dev/ttyUSB0`, or `/dev/cu.SLAB_USBtoUART` on MacOS. Note that the supplied docker-compose.yml assumes the Jade device is at /dev/ttyUSB0.
+The serial port pseudo-tty file for Jade access via USB is usually
+`/dev/ttyACM0` or `/dev/ttyUSB0` (or `/dev/cu.SLAB_USBtoUART` on MacOS).
 
-In order to have permission to use USB to install firmware, your user should be in `dialout` group on Debian
-based distributions. Other distributions may use a different group name: Check the group of the serial
-port pseudo-tty file using `ls -l` command to determine the required group, e.g:
+In order to have permission to use USB to install firmware, your user should
+be in the `dialout` group on Debian based distributions. Other distributions
+may use a different group name: Check the group of the serial port pseudo-tty
+file using `ls -l` to determine the required group, e.g:
 
 ```
 $ ls -l /dev/ttyACM0
 crw-rw----+ 1 root dialout 166, 0 Apr 15 14:37 /dev/ttyACM0
 ```
 
-The group name (`dialout` here) is shown after the owner (`root`). You can check that `dialout` appears in your user groups by running:
+The group name (`dialout` here) is shown after the owner (`root`). You can check
+that `dialout` appears in your user groups by running:
 
 ```
 $ groups
@@ -93,7 +84,70 @@ sudo usermod -aG dialout $USER
 
 You should then login/logout or reboot for the group changes to take effect.
 
-# Build the firmware
+**NOTE**: For docker builds no group changes are usually required as the
+docker image is privileged.
+
+You should set the environment variable `JADESERIALPORT` to the Jade USB
+device to default its value when running development scripts.
+
+## Docker build environment
+
+NOTE: MacOS users should set up the environment locally as detailed below to
+avoid issues with device access. For more information see
+[this article](https://dev.to/rubberduck/using-usb-with-docker-for-mac-3fdd).
+
+Blockstream provides the `blockstream/jade_build` docker image which provides
+the idf tooling and other dependencies required to build. To run a shell inside
+the Jade development builder, use:
+
+```
+docker run -it blockstream/jade_build:latest bash
+```
+
+Run `get_idf` within this container to enable the idf tools.
+
+Alternately, the `docker-compose.yml` file in this repository can be used to
+work on the current respository source code from within the `jade_build`
+container.
+
+```
+$ # Build the image and run a shell inside it
+$ docker compose run dev bash
+(docker)$ Set up idf environment
+(docker)$ get_idf
+(docker)# Make the serial device available to internal scripts, for example:
+(docker)$ export JADESERIALPORT=/dev/ttyACM0
+```
+
+You can then build and flash as detailed below.
+
+## Local build environment
+
+Install the esp-idf SDK and required tools. From a checked-out Jade
+git repository, run the following commands:
+
+```
+$ export ESP_IDF_BRANCH=$(grep ESP_IDF_BRANCH Dockerfile | sed 's/.*=//g')
+$ mkdir ~/esp
+$ cd ~/esp
+$ git clone --recursive https://github.com/espressif/esp-idf.git
+$ cd esp-idf
+$ git checkout $ESP_IDF_BRANCH
+$ ./install.sh --enable-gdbgui esp32 esp32s3
+$ python ./tools/idf_tools.py install qemu-xtensa
+```
+
+Set up the idf environment to make the `idf.py` command available,
+and then install the Jade dependencies into the idf environment:
+
+```
+$ . ~/esp/esp-idf/export.sh
+$ pip install --require-hashes -r ./requirements.txt
+```
+
+You can then build and flash as detailed below.
+
+# Build The firmware
 
 First, you'll need the Jade source code including its sub-modules checked out:
 
@@ -103,35 +157,34 @@ cd $HOME/jade
 git submodule update --init --recursive
 ```
 
-Choose your configuration. For Jade development, the script `tools/switch_to.sh` allows
+Choose your configuration. For official Jade devices, the script `tools/switch_to.sh` allows
 choosing the device and features you want. Run `tools/switch_to.sh --help` to see the
 available options. A standard development Jade Plus build for example would use something
 like:
 
 ```
-./tools/switch_to.sh jade_v2 --dev --log --jtag [--noradio]
+$ ./tools/switch_to.sh jade_v2 --dev --log --jtag [--noradio]
 ```
 
-
 For other devices, copy (and modify if desired) a suitable config from the `configs`
 directory to `sdkconfig.defaults`. You should also run e.g. `idf.py set-target esp32` or
 `idf.py set-target esp32s3` once initially to ensure you are targeting the correct
 toolchain for your hardware. So for example for the TTGO T-Display:
 
 ```
-cp configs/sdkconfig_display_ttgo_tdisplay.defaults sdkconfig.defaults
+$ cp configs/sdkconfig_display_ttgo_tdisplay.defaults sdkconfig.defaults
 ```
 
 To build the firmware, run:
 
 ```
-idf.py all
+$ idf.py all
 ```
 
 To flash the resulting build to your device, run:
 
 ```
-idf.py flash [monitor]
+$ idf.py -p $JADESERIALPORT flash [monitor]
 ```
 
 Some hardware configurations (e.g. M5StickC-Plus) may not support the default baud
@@ -139,7 +192,7 @@ rate and so won't be detected. If this occurs you can force a specific baud rate
 for flash/monitor by using the `-b` argument, e.g:
 
 ```
-idf.py -b 115200 flash monitor
+idf.py -p $JADESERIALPORT -b 115200 flash [monitor]
 ```
 
 If you have errors relating to unknown bytes when flashing, place your device
@@ -161,14 +214,18 @@ Beyond the build configurations in the `configs/` directory, you can edit the co
 manually with the `menuconfig` tool:
 
 ```
-idf.py menuconfig
+$ idf.py menuconfig
 ```
 
-Note: for any but the simplest CI-like build with no GUI, no camera, no user-interaction etc. it is recommended that PSRAM is available and enabled.  ( Component Config -> ESP-32 specific -> Support external SPI connected RAM )
+**NOTE**: for any but the simplest CI-like build with no GUI, no camera, no
+user-interaction etc. it is recommended that PSRAM (available under
+`Component Config -> ESP-32 specific -> Support external SPI connected RAM`
+is available and enabled.
 
 # Run the tests
 
-Virtualenv and bluez-tools are required, you can install them on Debian based distributions with:
+Virtualenv and bluez-tools are required, you can install them on Debian
+based distributions with:
 
 ```
 sudo apt install virtualenv bluez-tools
@@ -177,18 +234,19 @@ sudo apt install virtualenv bluez-tools
 Then to run the tests:
 
 ```
-cd $HOME/jade
-virtualenv -p python3 venv3
-source venv3/bin/activate
-pip install -r requirements.txt
-pip install -r pinserver/requirements.txt
-
-python test_jade.py
-
-deactivate
+$ cd $HOME/jade
+$ # Create and activate a Python virtualenv
+$ virtualenv -p python3 venv3
+$ source venv3/bin/activate
+$ pip install -r requirements.txt
+$ pip install -r pinserver/requirements.txt
+$ # Run the tests
+$ python test_jade.py --serialport $JADESERIALPORT
+$ # Cleanup
+$ deactivate
 ```
 
-Note that the tests require a CI build; this is a configuration that automatically
+The tests require a CI build; this is a configuration that automatically
 accepts the default action without requiring user interaction. This is enabled using
 the `--ci` argument to `switch_to.sh` or by setting `CONFIG_DEBUG_UNATTENDED_CI=y`
 in sdkconfig.defaults.
@@ -196,26 +254,6 @@ in sdkconfig.defaults.
 Debug support is also required to expose debug functions for testing. Use `--debug`
 or set `CONFIG_DEBUG_MODE=y` to enable this.
 
-# Use docker
-
-If you are on MacOS, you are better off setting up the environment locally as detailed above, rather than trying to get access to your device from the docker container. For more, see [this article](https://dev.to/rubberduck/using-usb-with-docker-for-mac-3fdd).
-
-The supplied docker-compose.yml assumes the Jade device is at /dev/ttyUSB0, but note that it may instead be e.g. /dev/ttyACM0 (or have another numeric suffix or path depending on the host operating system).
-
-The build steps within docker are the same as detailed above, e.g:
-
-```
-(local)$ docker-compose up -d
-(local)$ docker-compose exec dev bash
-(docker)$ ./tools/switch_to.sh jade --dev --log --jtag [--noradio]
-(docker)$ idf.py all
-(docker)$ idf.py flash
-```
-
-The docker-compose.yml also mounts the local git repository so that it is the
-origin of the repository in the docker.
-
-
 # Emulator/Virtualizer (qemu in Docker)
 
 The following will build a docker image running the headless ci-test (approves every request):