Thanks, Nellie and Happier.
On balance, DH is so apprehensive about this procedure, it's emphatically worth the cost of an overnight stay to remove the anxiety he has about the logistics of this. (It's what contingency savings are for!)
I should say that part of DH's mental frame around this is because I've been asking him to take action on a couple of health points for a couple of years. He kept delaying it until events have overtaken him for one item. Apparently, he had quite a vent about this to his psychologist who's been supporting him on 'the path to understanding what it means to be an adult' (from finances and budgeting to health).
We'd been planning a short break for later this year. If we go ahead and book anything, I'll make sure it's only if we can cancel it. (We've had enough difficulty trying to organise the blood tests and other bits and pieces DH needs ahead of the procedure. As it is, I'm never confident these things will go ahead on the day. As it is, I'm booking the overnight stay with a cancellation option, even if it is more costly.)