Where have you had success looking for grants for small enterprises in UK?

You may want to check out the search on this site grants http://businesslink.gov.uk/london.html

About this directory

The directory allows you to search for possible sources to initiate the development of small businesses. The database contains grant and support schemes from central and local government and private organizations.

Consider this

Remember to apply for a grant can be a very complex so it might be better to have a trusted financial advisor (ideally an experienced friend) for help and advice in the application.