In the four weeks it has taken Santander to send me the login credentials on paper for a new savings account, they are no longer the best deal for a savings account, so I'm going to close it unused.
A prior bad experience with Santander for a current account made me decide "never again", but I thought for an instant access savings account, "what can go wrong?"

It's not terrible, just unsatisfying. I'll happily go another 10 years without looking at them again.