Happened to me twice.
Nat West account first for about £400. I got a crime number, gave it to the bank and had my money back in about 4 days.
Second time, with RBoS, they actually called me to tell me my card had been used fraudently, for about £800.
One conversation, Them 'was it you'....me 'no'..them 'OK, we have refunded your account'