Ok so I've just done a quick search on here....
It seems the consensus is that they're quite collectible but better left 'mint in box' as they shoot, well, crap.
I think I'll be leaving that one on the shelf, especially at £320. If anyone is interested, it's with Philip Webster Gunsmith in Wymondham. As I said it's on a commission sale so I'm guessing Philip didn't set the price and it may be negotiable...