Dear Gabriel,
Your best bet is to phone the University of London accomodation office
forthwith and they will give you the telephone numbers of the halls that
do so. I managed to get bed and breakfast close by St Pancras at c.20
pounds a night two years ago, and while the bathroom facilities were
communal and spartan, they were also clean and adequate. There are about
4-5 halls of residence close by the British Library and I believe they
all rent rooms out during the summer. Many summers ago, when I was a
penniless graduate student, they also gave me a discount, but I don't
know if they still do.
Daniel Szechi
Auburn University