I’m not going to name names:
I did one the other day, the people who charge £99 a day, very good trainer, I’d recommend him to anyone, but too pricey, (my employer paid for mine)
My buddy did one with Big Name Driving Agency. He said it was rubbish, trainer gave him false info that could easily lead to infringements, fines, penalty points etc. When my (very knowledgeable) buddy corrected this rubbish trainer, they muted him 
There’s plenty of others running them at around £70ish.
These companies still have staff to employ and overheads, that’s why they’re not going to run them for next to nothing.
Some are limiting the courses to six people, some are not - mine had 23 participants and it worked fine.
I’m not going to fall into the trap of advertising, but I’ve already booked another course with a company I’ve used (in a real classroom situation) before, and after talking to them on the phone I’m confident they’re making big efforts to provide a decent quality session, knowlegeable trainers who won’t lead you astray, and a not-too-unbearable 7 hour session, which is pretty much all anyone can hope for.