Managed to get the BBC Model B emulator to work after an hour or two of reading and careful installation.
Using Windows 7 I had to use the Zadig method to get my MyStorm to be recognised by dfu-util in Windows. Flashing the .raw file was then straightforward.
Initially my 23" LG TV with VGA input wouldn't accept a 50Hz input, but a £9.99 Amazon VGA to HDMI Converter (which will also inject stereo audio from a 3.5mm jack) I had kicking around converted the 15.625kHz SRGB to HDMI in a format that the monitor would accept.
First two keyboards I tried with proper PS2 connectors (cheap no-name mini keyboard and a genuine IBM Model M from a genuine PS2) didn't work. 10 year old Microsoft USB Media Keyboard with a purple USB to PS2 converter worked fine.
My Sony UHD TV and Denon AVR don't like the output of the VGA to HDMI converter, but I also have a Composite/SCART/HDMI to HDMI converter (for frame rate conversion, audio extraction etc.) and that converts the 576p50 signal it thinks it is getting to 1080p50 that the AVR and TV are happy with.
It's not perfect - the Mode 7 interlacing is a bit funky - but until I get a VGA->SCART cable it's fine!
For info I'm using proper Digilent VGA and PS2 PMOD boards. Just need to build a little audio cable to header.
Very happy bunny!