UK. I haven't used or carried cash here for about 3 years. Other than a really inconvenient time someone gave me some for one of my kids and I had to pay it in.
However, if one private person is selling something to another private person, and they don't know each other, then it's nearly always cash because most people aren't set up to receive digital payments, don't want the hassle of setting it up just for one odd item, and in any case wouldn't trust the technology and companies involved for a large sum so people quite frequently pay for a second-hand car in cash if it's a private sale.
In London. You can do just fine with only a card. Quite a few coffee shops and lunch places only accept cards.
In Nottingham I've not seen a place that only accepts card. The Buses still accept cash