All - Thanks very much for the input...
I had put that budget together based on 2 things - estimates I had seen, and the actual offer I had received. I had planned on living probably in one of the more distant zones, but based on everyone's feedback, I declined the initial offer, as the budget I posted was basically what I would have had to live with. Thanks to you guys, they renegotiated and offered me another 9k/year, which should allow me to work everything in, including much higher living expenses, as you all have suggested. I will probably still put together another budget shortly and post again. For those of you who have asked, I am expecting to work in Southwark, although I may also work in the city itself, and would be living somewhere a bit more distant (originally had thought Heathrow might work out okay, but now given increased budget, may try to get closer). Thanks for all the input...although I do recall seeing somewhere a link for estimating taxes - if someone could repost that, I would be extremely grateful.