What you shop for and where you shop for it usually determines how you will pay for it. In a street fair or a flea-market cash is king. Folding paper and clinking coins are usually the means of exchange at these events, though I did see a jewelry vendor once taking credit cards with a satellite connected credit card machine.
For most casual or small item purchases shoppe keepers would usually rather see you pull a few pounds from your pocket as a credit card transaction for only a small total still gets the shoppe keeper a fee from the credit cards clearing houses.
Some even limit the minimum amount you can charge on your card. For sizable purchases, a credit card is expected and that expectation rises with as level of purchase price rises.
For instance buying furniture or appliances only see cash for deposits or down payments while the complete transaction will probably go on a credit card either one of your choosing or an “in-house” card that many times is just a standard card with a store logo attached and separate billing from your normal card even if its from the same credit company.
When you get to the big purchases like fine art or jewelry, the exact type of credit card expected even varies. For instance, a 20,000 pound diamond ring is expected to be paid for with a credit card of the Platinum or Gold variety.