I had a lovely TT engineer visit on Saturday and he gave me a new youview box, the DN372T, and a new router, the HG633, and no more problems except that my daughter now can't get a wireless signal one her iPad upstairs in the room above the router, whereas she could with the old 533. It's probably best if I open a new thread on the Broadband section.
The Youview box is a dream compared to the old one and reacts so quickly to the remote control!