Hello @Hugo1009
I've just been onto your calendar and there are no rule sets applied to Christmas and New Year - just a 4 day minimum so anyone can check in on Xmas day and New Year's day!.
I have been able to do the same thing you want using the Professional Tools but just created a Xmas rule (no arrivals Xmas Eve ,Xmas Day and Boxing day in my case) and then another one for a New Year Rule:
In the example you give:
This is surely a bug. I want someone to be able to book for four or more nights, say from 22nd to 25th for example
It's normal that someone can't book from the 22nd to 25th December because that only makes 3 nights as you have ruled that the 25th and 26th can't be a check-in date but they should be able to stay until the next available check-in date.
If you go onto my calendar as a guest, you'll see that the 24th, 25th and 26th December are marked as being "host unavailable so no check-ins, no check-outs possible. If someone wants to arrive on the 22nd December, although I have put a 3 night minimum, they won't be able to stay just 3 days because of my rule sets and the next available date to show available will be the 27th December
Hope this makes sense
Joëlle