Yes it is legal. It sounds like a prewar Junior so pics would help. As for selling it you are on the right site.
I would like to ask for first dibs but I think I might be breaking the rules!
Privately owned airguns can be sent through the post, I suggest you post some pics on here to get opinions on valuation, cost of postage will be about £5 so no big deal.
Oh, by the way it is Webley, not a football pitch!