I can really see a problem shortage of suitably qualified instructors at CPL level in this country shortly... if not already. My hunch is much more advanced training will be moved overseas with a small core of IR instructors left creaming the milk off the many in the UK.
Rarely does a newly minted CPL/IR fATPL holder decide to forget airline flying and stick with instructing long enough to aquire the associated ratings to instruct advanced students.
What background have most advanced instructors come from? The answer is probably via the old CAA CPL route. How many people still go through this route as a viable means of obtaining pilot work? Not many I bet.
VFE.