Latest news update - 'phoned Nationwide. Excellent woman (Thanks, Tracey) on customer services, despite the late hour.
Confirmed yes, there are current problems worldwide in using NW cashcards in ATMs. It is because Mastercard/Cirrus are globally in the middle of updating all their ATMs. NW have no control over Mastercard (presumably they as many others are tied into a contract). The problems seem not to be software-based, but network-based - I assume as they upgrade sections they switch off and on parts of the network, which will have a domino effect and block communications. (Techies can correct me but I think that's the gist of it.) NW's latest update from Mastercard was as far back as May. Not good enough, but not NW's fault.
In addition, my card (but not my husband's) had just been "restricted" - on the grounds that it kept on being put into different ATMs but without cash being withdrawn....... (Grrrrrrrrrrrr.) The fraud/restrictions team had been in an emergency meeting for 3 hours (and as she and I spoke) which was expected to last until 11.00pm. (Presumably because all of us frustrated NW ATM attempters abroad had been restricted, and someone bright somewhere realised something was wrong?)
She promised someone would phone back. In fact, she did herself, 2 minutes afterwards - fraud team out of meeting - my card now de-restricted - still be hiccup problems with non-uk ATMs for a few months though.
At least we know what's going on now. But yes, watchdog or moneybox should take it up. Mastercard is the enemy though, not Nationwide.
Any more thoughts, out there?