There are a few message boards and websites that give great info on legit work at home jobs...but most are only for USA or Canada from what I have seen..
Workplacelikehome.com is a great message board and you could def ask if there are any UK jobs... also
http://www.ratracerebellion.com/JOBLEADS.html Click on the category and one of the things it tells you is where the company hires..ie. under customer service it looks like only
http://www.hirepoint.com/athome/index.html hires from UK...
Arise has a UK division but it requires you to setup a corporation for yourself ..
http://www.arise.com/in-the-united-kingdom/
HTH