As you are managing to keep to a 5-hour window I would try and stick to it. Mine started at 1700 - 2200 but is now 1500 - 2000 but I often don't eat past 1830 or 1900.
As for holidays, when I did 5:2 I just gave up for the week, but I think I will manage to Fast-5. We self-cater and usually lunch out when,sightseeing; OH will have a snack in the evening.
All the best
Barbara