We have National Trust membership too, but over here in Northern Ireland there are really only 2 places with paid entry where we get to use it. Mount Stewart, and Castle Ward. Thankfully Mount Stewart is pretty close to us so we get our money's worth from going there alone.
I know somebody less than ½mile from here who was given National Trust for Scotland life membership as a 21st birthday present. That gains him entry and free parking in England and Wales, too.
I gave one of my daughters NT membership as a Christmas present two years ago. Even in free entry premises, it would have allowed her not to pay the parking charges. Because of lockdown she never used it