So just spent quite some time trying to sort out all the cable wiring behind the entertainment centre, with the result being, we can't find the tv antenna amp. There is no indicator light lit on the antenna itself and no tv signal to tv. Its a Dantronics UFO and it all appears to be factory install judging by cable idents.
I am assuming the cable labelled boost is coming from wherever that amp is .Checked continuity from antenna to boost cable ( ok), v/berth (ok) and input from transom (ok).
I did actually look in there, but was full of stuff, maybe I missed an access panel.....that boost cable appears to come from that area, I have this feeling they have put it behind the fridge where they would of had 110....hope not, could of been mounted right in the entertainment centre ( oh well there is no explaining to engineers).
There is one other panel which is in the shower, but all very nicely sealed around the edges....I may give up.
And now the rest of the story......thanks Kenny...once we removed everything, seems I missed the tab on the one side that you pull to get the rear panel off and voila the amp, which had no cable connected , they were joined together so put them back on and we have one tv channel. So another mystery solved.