I use Metronet (
Click me!) who have a very good system
Basically, I pay a nominal amount per month (£13.75 for a 1MB service). For that, I get around 2GB of downloads. You do not get cut off at that point though. All that happens is that you pay 25p per 1MB downloaded above that 2GB. When you hit 8GB, you pay no more. Again, you do not get cut off. You merely hit a limit on the amount you pay. At that limit, you will pay £26.75. You'll never pay more than that £26.75, but may pay as little as £13.75. And you never ever get restricted!!
You are also only tied in for 3 months (most companies make you sign a 12 month contract).
Now for the downside. You do not get a modem or free connection. The connection will cost you £70 (which is how much BT charge all broadband companies per connection) and you can pick up a modem for around £20 from Dabs (
Click here) - or at least, you could around 18 months ago. I haven't checked prices recently, and actually use a wireless router and modem combined, which cost around £80, but I doubt you'll pay much for a standard broadband modem.
Funny thing is, a couple of weeks ago some bloke knocked on my door one evening trying to sell me his broadband service, and ended up making notes on what I have cos it was a much better deal!!! Lol