Whopity has it, the CAA have delegated all of this to ATOs now.
The idea is that they assess your training needs, come up with a course to suit them, and then you pass a proficiency check.
So if you're Mr Sunday Flyer, only ever flew 20 hours post PPL and haven't flown for 10 years, the school say you'll need to do 15 hours or whatever they deem necessary to get up to speed. Once complete they give you a certificate which you give to an examiner who tests you.
If you're a current ATPL(H), they'll probably just get you to do a few hours and if all is well put you forwards for the check.
This is how it all works in theory. In reality, ATOs often aren't organised enough to sort it out, and probably don't come up with a proper training plan, so you just do the usual few hours of repetitive stalls, a brief bit of Nav but never enough, a few circuits, and send you off for an examiner to sort out. All good fun!