Ummm
Well I've already fiddled about with the rf on the vcr and it appears to be on ch28 according to the tv's tuner.
It certainly appears that the vcr and the stb are not on the same channel, well not now anyway...
I'll nip out shortly and see if I can get one of these y piece splitters for the rf and another patch lead.
Hopefully that might help.
What is so annoying is that everything works perfectly well on it's own, but connected together something seems to be interfering with something else.