So I took it back to the Telecom shop where I purchased it from but they said they couldn't/wouldn't do anything. All they said was that I had to ring some 0800 number and it was nothing to do with them. I told them that as a retailer selling a product they are obliged under the consumers guarantees act they have to support it. They told me thats not how it works with electronics.
Anyway I left the Tivo with them and made them give me a receipt to say I had given it back to them.