To put some perspective on your comment - although there are some ISPs which do have a cap of 15-30, or even 50gb
Zen Internet is a good example - it costs a bloody fortune, but you can download however much you like. If the ISP offends you after, you can also leave with 1 months notice. There is also no secret cap that I am aware of - and I downloaded several hundred gigabytes in some months.
Virgin's cable service is also uncapped, and it is significantly cheaper, although I don't know if they have an secret cap like some ISPs do.
The difference between the UKs internet and the US's internet is that the UK has competition, and the US has monopolies and duopolies for service in a given area. We might have to pay more - but you *can* get what you want.