UPDATE: I'm thrilled to say that service was restored at 8.33pm. Others are not yet so lucky but things are looking good. The Digital Spy Discussion forums have the latest info.
Two hours laters when nothing had changed, it was clear something had gone horribly wrong. After a 40 minute phone queue wait, I was told that this affects EVERY TV Drive user in the country and there is no estimated time to fix. They hope that they can put things right within 24 hours but no promises.
Of course, if they've borked the firmware with a bug-ridden update - and pushed that to every TV Drive in the country then the fix might take a lot longer and be much more expensive...
Wonder how long I'll have to wait until I can watch TV again?