I understand why bt have that 80/90/100 cap but untill someone actually take them to court over the "unlimited" advertising they, and most other isps, will continue to use it.
Being fair, 90gb really is a joke these days. With browsing, afew downloads, hd tv (iplyer/whatever), games, steam, patches, youtube etc is very realistic of a family of 4 to hit 5-600gb a month.Talktalk is possibly the worst isp out there but even their fup on their top package is 500gb. I should point out, for the unsympathetic/d-grade mathematicians , that a line synced at 24m will hit 150gb in ~16 hours, not exactly 24/7. A more realistic 10-12m (which most people get) is 30 (30/30=1 hour per day). I don't want to know how much data you can shift on a 50m virgin line but even that, globally speaking, isn't that quick.
The simple fact of the matter is bts infrastructure is many years behind the rest of Europe but our usage is not and people are starting to realise that.