Thanks yo Steve (G8XPZ) for helping me to test the Knucker. So I know that bit works.
I have also powered up the raspberry Pi and that is working. It happily runs the Ryde software.
However there is a red screen problem about source not connected.
Having done some reading it seems that the Knucker doesn't run with the lovely Ryde box that I have just repurposed an old commercial set top box for.
Am I right in thinking this is correct and do I now need to build a PicoTuner instead?

Many thanks for any pointers.
Neil.