Slide out fixed island bed frame

Hi folks,

My wife Sandra have a Lunar Clubman Si and we would like to replace our bed frame with one of the slide out ones that we have seen on some of the newer vans.  I have seen a couple for sale but they always seem to be a long way from us. Can any of you knowledgeable folks recommend anywhere near Bristol that might have such a thing from a salvaged caravan?

I know the sizes may differ and we have the folding mattress as I converted our frame into a folding version but it's still a hassle lifting the mattress for my little lady.  I am quite capable of "Adjusting" the wooden box that the frame sits in if need be so we just need to locate a frame. 

Thanks in advance,

Richard.