According to CHAIN
... 483 people were sleeping rough in London in 2008:

tinyurl.com/ktg29l

An brief explanation of CHAIN: "CHAIN is the Combined Homeless and Information Network. It is a database for people who work with rough sleepers and the street population in London. The system is used to help workers share information to ensure that they act as quickly and effectively as possible to help those they encounter. Reports based on information held in CHAIN help decision-makers monitor the needs of rough sleepers in London".

Not all rough sleepers want to go into hostels - they have often had bad experiences in them (violence particularly) or are alcohol dependent and sober but cannot get a place in a "dry" hostel.
( lkjshaglkasjdhglkhjz lkcvl; g;aodh;owih, Tue 7 Jul 2009, 8:27, Reply)