I picked this up off the Telegraph website this morning:
Cross-border rules after Brexit mean British banks will no longer be able to provide UK banking services to expats resident in EU countries unless they set up a separate legal entity in each region. This creates added costs for the banks and will result in services being cut in countries where it no longer makes financial sense to operate. Each bank will make its own decision on account closures according to the amount of business it does in each EU nation and the cost of keeping services going.
Customers say they face a 'lottery' as some banks cut services in their country of residence while others keep them going - and not all banks have announced their intentions yet.
Just a thought. A while ago I opened a Transferwise borderless account and deposited a token amount in both sterling and euros, just as a back-stop in case I had a problem with either UK or Spanish bank, and it looks like I may have to start using that.