To make sure I understand, Mastercard illegally overcharged for credit card processing, and merchants passed the charge onto consumers, so consumers have standi

To make sure I understand, Mastercard illegally overcharged for credit card processing, and merchants passed the charge onto consumers, so consumers have standing to sue Mastercard. If I've got that right, can someone with an understanding of British law explain how that works? In a case like this in the US I don't think consumers would be able to sue a card issuer.