Thanks for all the replies, we took the plunge and bought one locally on ebay.. it was stated as the reverse not working and after enquiries the seller thought it may be the reverse switch so we had a look at it and all other gears were fine and it runs smoothly.
So £1100 later and we picked it up very pleased with the bike, had a look at the reverse cable and it was loose, tightened it up and bingo! we have a fully functioning quad!
I am sure if it had been advertised as full working order it would have gone out of our price range so on this occasion we were very very lucky
off to play on it now!