I brought FTL for 2£ but didn't receive the game.
Also got a free copy of Mount and Blade but didn't receive that either.

What and how?

Did you receive the emails about the purchase?
Did you hide all the free games your account has?

Oh and try refreshing your account: https://secure.gog.com/account/refresh

For "Mount and Blade" it will take a while until the game will be added to your library (I had to wait few hours).
For the game you purchased - check if you received any e-mail about your purchase - if GOG sent you confirmation but the game is still not in your library than just contact support.
If you didn't received confirmation please check if your credit card (or PayPal account) was charged for your purchase. If you was charged than once again - contact support. If you were not charged than something went wrong and the process of purchase failed.