You can do a 5 day course to become a Manual Handling instrutor. Lots of compnaied offer it. See [broken link removed].
Nifast also do a course setting you up as a trainer in defibrillator use which might be useful given the number of defibs springing up around teh country.
No connection to Nifast, have just used them before.
It's difficult to become a first aid trainer, I think you need lots of experience and approval from the HSA to train.
There are too many safe pass instructors at the minute so I don't think that there's much profit in it. Again I thnk you need to demonsrate some experience in the sector and apply to FAS for training.