We've only ever been outside of school holidays. We went in November last year for the Christmas thing, which was lovely but didn't feel any busier than usual.
We have a break booked for November this year with my whole family which may have to be postponed because of someone's cancer treatment. My Mum has suggested paying the extra and going in the Summer holidays?
Is it noticeably busier? We never eat out and don't often do any of the paid activities, just swimming (which is back to no booking now) and the play parks, walks, cycling.