Are you actually in London or just outside? I've travelled a couple of hours to pick up a hamster before
. Although that was by train. If going by car then it helps to have two of you, so the one in the passenger seat can hold onto the pet carrier. I always hold the pet carrier on my knee (as a passenger) with a blanket over it so it's cosy and dark and helps block out traffic noise and flashing lights etc. They usually just go to sleep
Driving, two hours is a bit far though - to go and come back again. For you rather than the hamster.