Prop Swinger - If I read your post correctly, you are saying that paying the instructors for training in a BGA enviroment is not a commercial transaction??? The BGA is clear when it states non commercial enviroment.
If thats the case then they have no need to declare the income and pay any tax....
The real question is simple - if someone pays a club to gain a NPPL on a motorglider and it uses BGA instructors who do not hold CAA / JAR FI ratings (just BGA ratings) then that is acceptable and legal - if so why do the CAA not recognise the hours towards the issue of an EASA or JAR licence in such circumstances?
With respect to the work on the aircraft under the BGA CAMO are ALL BGA inspectors licenced by the CAA as aircraft engineers?