There are some schemes, nothing quite as advanced as Y combinator. - Seedcamp http://seedcamp.com/ - Launch48 Launchpad http://www.launch48.com/launchpad/

But there are lots of places one could hang out and work on an idea: - Accelerator London: http://www.accelerator-london.com/ - London Hackspace: http://london.hackspace.org.uk

Shameless self-promotion, have a look around here about London based startup resources / opportunities (look at the schmoozing list!) - http://londonstartups.co.uk/