I have done this a lot in reverse during my working life. I lived in London and travelled north, Newcastle, Aberdeen, Barrow etc. during the week. Travel as light as you dare. You only need to carry four shirts and four sets of underwear, you'll be wearing one. Along with a pair of jeans and a couple of tee shirts for the evenings and your toiletries, that should be enough. Remember you can always pop in M&S if you need something, dont carry it if you dont need it!!! Depending on where in London you will be working, dont try to live on top of work if downtown, too expensive. The transport system in London is really good, look to stay in the suburbs, a much cheaper option.