BEagle,
If I may address your last post, what a load of twoddle!!!
I believe the check pilots, quite coincidentally, do hold instructors ratings or higher. The system has been in place for, oh, nearly fifty years and has worked well, the Tiger Club having been a breeding ground for aerobatic, racing and display pilots for most of this time. You'll want to check your history books to see the role of the Tiger Club in UK GA.
The Club has a system which imposes a higher standard than the law requires.
Type specific training, aerobatics and formation flying require no special qualification of the teacher, there being no specific qualification to receive. You 'could' teach yourself.
Whilst the check pilots hold professional licences none of them charge for their time or experience. Put rather romantically you could say that they are 'giving' back to a club which has been so generous to give them those skills in the first place.
Perhaps, in this cynical world, it is hard to believe that there are people who just love flying old aeroplanes.
As for "To my mind, anyone giving aerobatic instruction to a licence holding pilot must be AT LEAST a CRI(A)"...I nearly fell of my chair at such blind nonsense!
Instructors building hours to get their careers started seems to me like the one-eyed man in the land of the blind.