Then, shops don’t accept US dollars.
No, it’s a different country, we use UK Pounds (£). Surely that would be one of the first things anyone travelling would know. You are not in the USA anymore. They must realise that? They must have passports.
People use cards these days, and then who cares what the currency is? It’s only of concern when you get back home and see your bills or statements. They convert for you.
Actually though, I haven’t shopped at Harrod’s for a long time but I believe they, and some other places, did and maybe do accept dollars and Euros. The exchange rate, I am sure, was poor, but you’re paying for the convenience.
Payments are confusing as you don’t know what the tax is.
No, it’s all added into the final price. No complicated sums to work out. So much easier… You pay what you see.