Very interesting article by Reuters about this:
"Since Brexit, an EU-enforced cap on fees charged by card issuers is no longer in place in the UK.
The move by Amazon, earlier reported by Bloomberg News, has prompted the UK Trade Commission to call on the government to improve the UK-EU trade agreement and analysts to call on British regulators to look into the fees in the credit card market.
"If Amazon can't make it work, with all their resources and ability to navigate legislation to avoid costs, then small businesses have no chance and so the government must improve the UK-EU trade and cooperation agreement to keep British businesses competitive," said Tamara Cincik from UK Trade and Business Commission"
https://www.reuters.com/business/retail-consumer/amazon-stop-accepting-visa-credit-cards-issued-uk-bloomberg-news-2021-11-17/