Anyone who has used Costa Coffee T5 Arrivals and used either a Chip and Pin or a Contactless in the last few weeks. Check your bank statements for "O2 UK PAY & GO" transactions - typically £10 - £15 area - that you do not recognise. These would typically be 2 days after the legitimate Costa Coffee transaction. This is the fairly big Costa directly in front of International Arrivals landside.

[And a reminder that if using contactless you can pay with your card upside down and/or with your thumb obscuring the final digits]