Favourite UK airfield/aerodrome? Don’t have one; I view UK aerodromes only as locations for getting fuel – excepting my home base, none are a destination that I would visit other than the aircraft having a need (I’m a helicopter pilot not fixed-wing).
Favourite outside the UK? Visited several in other countries (and thought “this is nice; why can’t we have something like this in the UK?”)
My best pick has to be Fort Lauderdale Downtown Heliport (DT1) for it’s uniqueness and fun to visit. Large rooftop helipad atop a multi-story carpark (10 floors) in Downtown Fort Lauderdale, Florida. With a quick phone call you are given an elevator code to take you down to street level and then a short walk to the ocean front for a nice visit/lunch. Opening hours and landing fees: open 24/7, no landing fee and 4hrs free parking
https://www.flyfxe.com/operations/dt1-downtown-helistop