Should you accept it? Yes, anyone in the UK would lose out on revenue if they did not accept Mastercard.
Transaction fees: Lowest of all cards. Premium, business and foreign-issued cards usually incur higher fees.
Card readers accepting it: iZettle Reader, SumUp Air, SumUp 3G, Square Reader, PayPal Here, myPOS, Worldpay Reader, Barclaycard Anywhere, Elavon MobileMerchant
Acquirers: All (excl. American Express)