I've just been pointed at this thread, and it looks like I may be competing with Sam, and I don't have his Mojo.
I will say that you probably want to drive to Brum Sam, a kitten is not likely to stay that clean for the journey time from Birmingham to London, so you really wouldn't want to take it on a train.
With a car you can carry newspapers, and spare sleeping stuff (towels etc) that can easily be cleaned, because I suspect that they'll almost certainly need to be!
What's the panels opinion on a kitten that young? I work all day, so would have to go to work and leave the kitten to itself during the day. I've got a spare bedroom that I won't worry too much about accidents occurring in, since there's no way the kitten could have free roaming of the house when I'm not around. There are far too many ways to come unstuck when they're that young, and doing the cat curiosity thing.
I think at that age they are weaning, so can probably survive eating solid cat food, although I can obviously check that with the vet and the local cat bods (the woman in the cattery that Talisker used, is a bod in Croydon Animal Samaritans). I believe that generally at that age they're on some solid food, and some of mum's milk still, but I'm not an expert by a long shot.