I have always used Chris Potter's.
Not a huge gun selection but they will get in almost anying and price matched even mail order companies on all the air rifles I have purchased from them.
They even got me my Ben Taylor Cyclone.
Ignore their price tags, they seem to make up very high prices but will discount heavily.
I suppose it looks good in that way but if you do not know this they look very expensive.
They only seem to like .22.
Colin is very helpful, ask for him if you call in or phone.
Nick