Flatshare is good, and so is www.spareroom.co.uk. Although sharing with strangers can be odd (especially given PhD working hours!) you will save money with that rather than a studio (sharing the price of a phone line, internet access, tv license etc), so might be an option. I live with a friend who I met whilst doing the PhD, but she quit at the end of her third year. Its harder now given that she goes out quite a lot, and I get jealous! But its workable. And you might get a normal sized bed out of it!

Doh! I gave the completely wrong URL!! I mean't www.spareroom.co.uk also (not flatshare).

Often rooms do come with double beds/skytv/broadband, but pay the early bird subscription on the site to first dibs at the new adverts (it costs £7.50). At the moment there are quite a lot of families offering rooms because they can't pay their mortgages, and I'm sure they'd like a PhD student...although introduce yourself as a 'PhD researcher' to avoid the 'student' stigma.

I used uk.easyroommate.com (sounds like it's for people with dubious morals, but it's not!) and found a really nice room in a flat with a mature student who needed to rent a room to pay the mortgage. Have you thought about some kind of quiet excercise like yoga or pilates? You'd still be surrounded by other people but at least they wouldn't be making too much noise!