I guess there has been no major acceptance issues but even if there were any this will surely be good news as one of big banks will start issuing MC from next year.
Google āSantander strikes debit card deal with MasterCardā for the FT article below:
https://www.ft.com/content/7d6f5e48-4d53-11e8-8a8e-22951a2d8493
The one inconvenience I can think of is Co-op bank ATMs not accepting MasterCard Debit cards (only the bank, not the stores). Hopefully this will force their hand.
It isnāt that Co-op banks donāt accept Mastercard debit cards. Rather their ATMs are only connected to the LINK network, not the Mastercard network. Since Santander (unlike Monzo) are member of the LINK network I fully expect their mastercard debit cards to work on these ATMs without any problems, as they can simply be routed through the LINK network.