Rob,
That's really useful info.
I was concerned about topping up sims .
Me and the missus have got a sim overload at the moment one for each of the following BT(EE),giffgaff, 3 and vodaphone and the kids have got Tescos but I am trying to rationalise them .....Honest.
But the ASDA offer would definitely float my boat if you excuse the punš