Having just managed to get the CrossEPG downloader to work, by telling tuner B to loop through to tuner A, I can confirm that it finds 915 channels Now I just have to find out why I can't record one channel, whilst watching another I'll disconnect the cables tomorrow, check and replace them. I've a feeling it's something simple (a bit like me) a setting somewhere? rather than a hardware issue.
More likely to be LNB failure than wire damage, although still possible. You can swap port used on LNB to double check.
Niteowl (12-09-16)
Swapped my cables around this afternoon, putting feed A to B and vice versa, and changed my tuner settings to the same from "loop through to A" and it looks like it is now working A.O.K. crossEPG downloaded fine and I set one channel recording then switched channels and it switched
Many many thanks for the prompt and helpful replies, you guys ROCK