I know this isn't exactly a 'hostel' but it's the first time I got off a plane and didn't have a place to stay, meaning a hotel or friends house! This was a new experience for me.
Carr Saunders Hall has a great location, it lets to nonstudents during the holidays usually from the end of June to mid-September and sometimes over Easter break. I know it's a little more expensive but you can have a single or double for about 30 bucks a night. It includes all linens, privacy, great buffet breakfast, laundry facilities and did I mention location? :D Near the tube at Warren street, British museum, major bus stops, right in the middle of it all! I met a lot of nice people there, happen to be there during "9-11".
The number is 7323 9712