Actually not strictly true. Only the larger named ISPs (larger market share) have to comply. The smaller ISPs do not.
+£10 for 100Gb. +£20 for 200Gb. Not particularly expensive and considering it's a proper line, not some screwed up censored telescreen pipe, I'm not fussed.
They seem to price much higher for daytime use , which is when I would mainly use it (I work from home). 200GB of offpeak and daytime per month would be £332.00.
Besides, if everyone just switched to a "proper" ISP then they would be forced into compliance, the same as everyone else.
I can't seem to get more than 50GB per month with that (according to logs I shift 10x that).
Problem is that people will just go with whichever ISP is most popular and their friends are using or the cheapest. People won't generally sit and research all of their options.
Looked at the prices for Andrews and Arnold £25 per month with a download cap of 25GB. I would use that up in under a week.