The site has gone down, possibly related to a Hard Disk check we're running with Support. We had a SMART message about one yesterday, and they've been testing it since. It might not be related, but they're aware of the site being down again, so we'll be back soon(ish), with luck :)
EDIT 15:32 BST: I've got FTP and Control Panel up, and it looks like the site is waking up slowly too.
EDIT: 16:34 BST: I think we know why the crash happened, and now we have a couple of options of what to do about it. One will involve several hours offline, the other will require money. Was it ever thus?