I heard about this over the weekend and it took me by surpise. Mobile network operator "3" now offer the best value and most convenient broadband connection for a substantial segment of the UK market. It's HSDPA and functionally like a precursor to Wi-Max.
Attach this device to your PC/Mac via a USB port, and it will use the 3 mobile network to offer a (max speed) 2800/384 kbps connection. It's £10 month (18 month contract, 1Gig cap). It's a suitable replacement for both a light home-user, and as a replacement to the patchwork wi-fi network in place across the country for mobile users.
The revolution here is because it doesn't require a landline (£11 p.m. alone) . . . . BT now also require an 12 month contract for any new line connection and an installation charge of £125. That's pretty tough for a student or a short-term renter. You might think TalkTalk would be an alternative . . . but what they don't say is that they can't connect phone lines. So you've got to sign up with BT first. 12 months later, you can become a Talk Talk user.
For anyone who doesn't need a landline - this broadband is very affordable. And it's mobile.