• BT Openzone: £6/hr
• Tmobile: £5/hr
• ZiFi Zone - The Cloud: £4,55/hr, but you can also buy 30 minutes for £2.99

It's still horribly expensive, but considering that it didn't take much to compare the three services (all I did was selecting the different networks and check the default page), you get to woner who is paying BT.