Staywet.
Exactly the situation I was in. I was selling helicopter tours, and flight experiences and also did a bit of trading on aviation items. Unfortunately this was not enough to convince the VAT inspector dealing with my case.
Apparently recovering 'training' costs on a PPL is seen as self supply and not counted as training.
If you get your CPL and then register you should be able to claim back everything in previous 6 months, as at that point your are an 'employable' pilot.
I think at the end of the day it's luck of the draw. I just wasn't lucky...
I'll PM you details of an accountant well versed in this type of thing.