Having received my offers I tried to accept the free sim card for 12 months. Now as I already have a paid for Talk Talk mobile sim and they still sent me the offer I thought there would be no problem.
I finally admitted defeat after some hours on the 'phone being transferred around their system with each operator requiring all my details, then saying I couldn't have the card because I already have one of theirs, then speaking at my request to their manager who eventually agreed I could, then being transferred and waiting for 30 minutes before hanging up and trying again and their operator requiring all my details, then saying I couldn't have the card because I already have one of theirs, then speaking at my request to their manager who eventually I agreed I could, then being transferred and waiting......and so on and so on.
I am left with the idea that there is no real free offer and that I should simply cancel the present mobile contract and start again with a supplier who have their act together.
As to the main contract for the internet with Tiscali: Time for talk talk...but with a different supplier.