It has always been capped in the UK.
Most ISPs offer a variety of options, the lowest usually start at around 5gb the highest being unlimited. If you go over your allotted amount they charge you, its not much though about £1 a GB depending on the provider.
I have unlimited usage but I'm still bound by a fair-use policy. If I abuse the unlimited usage they will start to throttle the line during peak hours (4-8pm). What counts as abuse I do not know as I have never exceeded it.