With more and more people now carrying less cash, it might be time to give card payments a try.
None of the links below are recommendations or are in any way sponsored, they are just a collection of information currently available with what appears to be good practise and information.
Most if not all work off mobile phone technology plus there is a link to card readers that use a standard telephone line.

Mobile card payment providers UK

iZettle vs Square, Paypal, Worldpay & Sumup: 2018 Reader Comparison

(you do not need to fill in the question at thew top of the page)