Quick update for you, we do not have a dvd player or anything with a HDMI in and out so i tried it out on my sky+ box and got the preview no problems at all. The only thing i got warning wish was a red 'protected signal' which i would expect as it is satelite.
I will now try again on my xbox later this evening and hope ity will work, if not i can only put it down to 2 things really.
I am not using an official xbox hdmi cable, but i didn't when it was working before so cant see this being it
there are some settings on the xbox itself that i have not managed to sort out.
If anyone has any tips on the xbox setting it would be appreciated.
Main thing is i now know the RGC is working fine.
Thanks for you help gents and if and when i get the right settings on the xbox i will post here for other users