I would correct the London figure. DS shared a three bed ex-council flat near Great Ormond St, ten minutes walk to University, with three others and paid £185pw. He then had roughly £75pw which was a bit more than he needed.
There is a student London that can be cheap or free. Our observation is that more happens on campus, ie the Friday night disco, or societies. And he seemed more interested in going to Camden pubs to watch people in Korea play computer games (future Olympia sport?), happen upon free tickets to Comicon, or join a big gang from his course in China Town, than clubbing. Plus transport and small shops are open later so no need for taxis and takeaways, which, with alcohol, can quickly eat into student budgets. Overseas students seemed to be either super rich, or very frugal, which helped. He obviously mixed with the latter.
We gave DD, who is elsewhere, the same but she struggled in her first term. A couple of big nights out at freshers, then well over £300 for sport subscriptions and kit. She lived on the contents of the freezer in her last week - a batch cook of chili con carne. (Midway through I relented and ordered her a takeaway.) The second term has been a lot easier, and she has money left over. Inevitably and usefully students seem to sort themselves out socially by how much they have to spend. If you can blow £100 on a night out clubbing then you will make friends who do the same. DDs big night out is on a Wednesday following a match and this is where she has made her friends. They train several times a week and their budgets stretch to the occassional Spoons, but by and large they don't spend much.
The amount some spend is astonishing, and seems made up of student loans, overdraft, and parental top ups. I would not be surprised to hear that there are some payday loans in the mix. These will be the kids who stand out in the first term, who seem to be having the most fun. But roll on a uyear or so and I think DC may thank you for not having the funds to keep up with them.
Oh, and note some Universities have long first and second terms (circa 14 weeks if freshers is included) and short third ones, a lot more than Oxbridge's 8 weeks, and make sure your DC can shop, cook and budget before they start.