Hi Malcolm,
I also have a 60+ Oyster and I’ve never seen anything like a charge made to the credit card. However, whenever I use contactless I do get a 10p authorisation. This is replaced by the actual journey charge overnight, or a couple of days later if it’s an incomplete journey. I think it’s likely that your brother may have used his bank card at West Drayton instead of the 60+ card. I’ve done it myself a couple of times. I suggest he registers his bank card on his TfL account and then sees what history it shows. The helpdesk will refund the charge if one has been properly made. They don’t like doing it too many times though, as I found out the third time.