Try the Friday edition of London Loot. There's usually plenty of rooms in North London going.
If you've got a car then this is no problem. If you don't have a car then you have to get the tube to Edgware, take the 107 bus and then hike for about two miles, which in wet weather is interesting.
You can get a room in Hendon for a reasonable price but the night life is not up to much. Mind you, central london is about a half hour away by tube.