.........You agreed to the Telecom T+C's when you accepted the purchase, which was offered to you, for a consideration, and you accepted..........
IMHO I am sure that the CGA will determine there is a written contract here, that is no issue. The terms are quite clear. As have been posted here a few times.
Of course you now better than the bundle of docments i have relating to the Tivo - none of which mention Tivo T's and C's. I have already said there is reference to Freeview Terms - but not Tivo. The document is very clear with all the points with ticks and crosses next to them. Zero, nada zilch t's and C's you keep referring to.
So that aside it someone assert I have agreed them it will be for them to provide that evidence. Since you weren't there at the item of purchase the best I can suggest is you stop speculating.
Edit -oh and the way it works is I make an offer and telcom accepts it.