You might find that one of the bigger named places can do you a box.
When I had trouble with the gearbox on my Mk4 Polo, I phoned round a few places and found that the local branch of Mr Clutch would supply a recon box and fit it along with a new clutch for about £700. Which was about the best I found.
I too was told to steer clear of second hand boxes cos they can be more trouble than they're worth, unless of course you know where it's come from.
If you get your box refurb'd, at least you'll know that it's ok, and hopefully they won't have to replace much.
