csfta.co.uk should help you find a club, from your location I'd suggest Meon Valley would be your closest. Southampton Buccaneers are also close but they are more FT orientated, where as Meon are more HFT. However either club are welcoming of either discipline of shooter, it's just that they specialise in different areas. There's also BPARC at Basingstoke.
It really depends on what model and condition the Walther is in as to it's value.
BFTA/NSRA County Coach
CSFTA Chairman/BFTA Rep