MB Bank ATMs now charge 33,000 Dong ~£1 on a 1,00,000 withdrawal(previous posts on this forum indicate they didn’t, not sure when it changed).
VP Bank don’t, and they seem to have a good reputation (first choice for a few expats in Ho Chi Minh).
No issues whatsoever using the card simply as a card, Mastercard seems just as widely accepted as Visa. They have a slightly strange system of requiring both a pin and a signature but I’ve never found it to be an issue. I’ve also read somewhere that Vietnamese pin numbers are often 6 digits and you need to put in 2 leading 00’s, I never experienced that.