Personally I wouldn't risk my good name in having anyone other than a dentist carry out teeth whitening nor would I do the training for 3,000 never mind £800.
There was a therapist in my old salon who was being sued by a client for teeth whitening, she was adamant she wouldn't ever do it again and said she didn't want to do the training but the salon requested she did it. I felt so sorry for her. We had numerous calls from solicitors wanting to speak to her and I watched her face pale each time she was told there was a call for her.
I've heard too many things about law suits and sensitivity etc to think anyone other than a dentist should be allowed to do teeth whitening.
I think it's far better we advise clients that they are far better off seeing their dentist rather than asking us as beauty therapists if we do teeth whitening.