We just returned from 4 days in London where we (one couple and one single) stayed in a two bedroom apartment with two bath rooms. It's definitely something we will do again :-)
We found the apartment via http://wimdu.com. When we arrived they had switched us to another apartment, but it was just as good and closer to London Bridge. They had prepared a package with
- very detailed instructions how to find the apartment,
- two keys for the door and
- userid/password for the wifi.
I have never had so much living room in London :-) The price compares to a double room, but we had much more square meters and cooking breakfast and dinner (most days) ourselves saved both money and trouble (I really don't like hotel breakfasts).