My final thought on this subject is there's a vast difference between being expensive (or more expensive than assumed) and being "a rip off" (To exploit, swindle, cheat, or defraud).
I don't know the average cost for all 2 day ground schools, but market forces will determine if the "well known UK operator" has got the price right or wrong, for people that want an OEM certificate, as opposed to one which is just a good, but not issued/endorsed by the OEM's representative.
PS. I've today put 4 new Continental tyres on my car at £211 each, when I was offered similar Chinese brand ones at £120 each. You get what you pay for.