There's a nationwide issue with TiVo's connecting to the network. Recording and playback's okay, but On Demand, internet programme info and TV Anywhere App aren't available.
This Cable Forum thread has the latest info: VOD Network down?
ETA is 3.45pm on Saturday but there have been some signs of life already reported.
UPDATE 7.45pm in SE London: On Demand and TiVo services back up and running