BA are actually pretty generous when it comes to carrying sporting equipment:

http://www.britishairways.com/travel...t/public/en_gb

But as the link notes - they don't carry surfboards as part of your baggage allowance given that they are just so big and the terminals just aren't set up to handle them.

The do offer an option to ship them as unaccompanied baggage though, which is a bit more hassle for you as you'll have to drop it at the cargo terminal:

http://www.baworldcargo.com/products...cts/bags.shtml

I guess it comes down to what your board is worth and how attached to it you are.

For reference there's not a huge amount of surfing in London!