I used my Schwab debit card easily for purchases and ATM withdrawals all over Scotland in April, 2019. I was staying in the Haymarket area of Edinburgh for several days and I found several restaurants that were cash-only, especially sushi and some of the smaller ethnic places (which were all fantastic). I’d recommend having more like 50 pounds in cash on you but that’s just my opinion. I saw may locals using touchless pay systems like Apple Pay. My card will do that with my iPhone but I’d want to practice the operation first at home.
I can recommend the Schwab debit card. The account is tied to an investment account but you don’t need to use it that way. The debit card must be funded and the company alerted that you will be out of country. It is designed to work internationally without hassle and Schwab refunds most fees you might encounter at ATMs. (My post-Scotland statement shows zero transaction fees.) Easily researched, this card ranks high with travelers. Applying for the investment account to which the card will be tied will initiate a hard hit on your credit report, though.