I did a four day course with these guys: http://www.alanjohn.co.uk/ (they are based in the South so I don't know if that covers your area). They were very good and very thorough (I really hope I don't have to put some of the stuff I learnt into practice!)
Check out your local NHS ambulance service, as they often run first aid courses on behalf of companies - you may be able to slot in.
They're good because they will tell you why you should and should not do certain things in a situation, and they talk about the sort of mess they and the A&E dept. have to clear up when a well-meaning first-aider has done their bit.