BEagle, thanks and I am aware of the difference. I'm trying to keep the Harvard flights higher up the regulatory food chain.
I've not found anything that says a lesson has to be given in an aircraft that the student could later solo; so long as the lesson was teaching what it was meant to teach then why not? For example, if on an Ex 3 lesson the student wanted to experience aerobatics, as something they might like to aspire to later, and the normal LAPL trainer was a C172 then why not give that lesson in a Harvard? I don't think there is any regulation that says not.
It is very easy for a regulator to say 'no 'cos i don't think so and I've never seen that before'. Its much harder for them to say 'no' if they are asked to quote the regulation that supports that position. Just because something is out of the ordinary is not a valid reason for saying it is against 'the Regulations'.