I just thought I'd mention, although BT's capping is bad, it's not all that bad:

6. What happens if I exceed my monthly usage allowance?

In the unlikely event that you exceed your monthly usage allowance (remember these are more than enough for the vast majority of users) the speed of your connection will be reduced to 150kb until the start of the next month, when you monthly usage allowance will be reset.

If you exceed your usage allowance you will have three choices; you will be able to continue to surf and download at a reduced speed of 150kb - that's still three time the speed of dial up - for the remainder of the month, or you will be able to top up you usage allowance on bt.com by purchasing additional capacity at £1.95 per 1GB unit, or alternatively you may wish to consider upgrading to a higher usage capacity package.
So you still get a decent speed for web browsing- 150Kb, and you don't get overcharged unless you want to. You can buy additional GB if you want, and considering everyone is getting upgraded to 2Mb (I got upgraded to 1Mb today, but that's because my line can't handle more) I think BT is doing something fairly good.