If you Google First Aid courses London you will find all the training providers who offer this course. There are different levels - First Aid Appointed person (I think they have just changed the name to something else) which is a short course for people in the workplace etc who need to know first aid, and First Aif at Work which is the full-blown 3 or 4 day course for the people who are nominated first aiders in the workplace (and therefore might be responsible for a number of people). It's not cheap, but try St John, Red Cross, or any number of commercial training providers (most of whom often have beem ambulancemen etc.)