Update - 12 March 2010, 12:43am:
The problem has been caused by a massive power outtage in the Linford Wood area of Milton Keynes where the data centre is based.
Fortunately the power is now back online, however their internet connectivity has not yet been restored.
We expect the servers to be back online and fully functional within the next couple of hours, hopefully sooner.
Update - 12 March 2010, 11:34am:
Some of our servers are currently down and this is affecting some websites and email. The data centre is aware of the issue and are working on the problem. We will update this message when we have further information.