On autographs you rarely get bargains unless you know how to authenticate. If you bought it recently on Amazon you should be able to return it. How much did you pay?
£44??? Genuine examples bring about $700 to over $1,000. Why would you think there's even a shot that it's real at that price? When you make purchases like that you're encouraging the bad guys to do it again.
Flat-signed Obama is something I would steer far away from -- unless it's part of the "Promised Land" LE he did or you have supporting documentation, I would steer clear. Far too easy to fake.