The exact same thing happened to me .. I had £6k taken from my a/c over 2 days. If I am not using my card then it is in my wallet and it never leaves my possesion.
It seems I bought an expensive TV in Birmingham, had a meal in a riverside resturant on the Thames and then settled various utility bills in Coventry all in the same afternoon.
The best one was I paid an HMRC tax bill for some doughnut.
All the money was returned to my a/c by the bank within 5 days. Never heard another thing about it.