Thanks for the reply. It's a V6 box running the TiVo service but I always call it a TiVo. So the post should have gone into the V6 Box subcategory rather than TiVo Box.
So, as you're probably aware, it uses the Wifi router for on-demand content.
By "refund" I mean partial refund or credit on the next bill for lack of service, which Virgin Media have done before.
It did take a few days for the On Demand service to return to normal (after several hours of no TV/broadband/phone service) and it is working properly as I write this.