I am surprised that no one has ever recommended university rooms during the summer breaks.
Nearly all universities let out their student rooms. Most are single study rooms, but twin rooms and in some cases flats are available.
This is for the London Metropolitan University in the heart of the city.
We are open for group and individual bookings from June 27th till September 12th 2005. Our prices for 2005 for our single rooms are ��91 per person per week or ��23 per person per night.
A UK Google search for "university summer accommodation" finds many universities offering this.