I lived in the UK for decades, and I don't recall a place that only accepted debit cards. The fees are slightly lower for debit vs credit cards, but they're low for both types of card.
Plenty of places in Europe don't accept AmEx, it still has high fees.
It's true that Germans prefer cash, but that's not necessarily because of the cost of processing cards. Most supermarkets accept cards, but the average German uses a card slightly more than once a week.
https://www.euro-area-statistics.org/classic/payment-statist...
