I had lots of helpful advice on this topic, none of which I took. I waited for a reasonable period of time (around two or three weeks) and had nothing but a receipt confirming our card had been refunded.
So I emailed Sir Terry Leahy, CEO of Tesco. On 20 January having had no response or acknowledgement I sent it again. This time I received an email from a PA or assistant saying my email is receiving attention.
Watch this space.