We have the Dormobile roof and in summer a roof box on the cab roof so were are 2..2 M and don't fit in most car parks. I use google street view to check, I also phone the local authority if its critical. Some are very good (Hampshire, they know all the heights and have a few spaces with no height restriction) but most have no idea. I have a sign "too high to get in car park" with my mobile number and I put this in the window and park on the verge. Sometimes I'll buy a ticket form inside the car park and point out that I'm not avoiding paying, just being discriminated against but for the most part I have my list of "known good" car parks. If you look at the New Forest some car parks have height barriers, some do not, its case of doing a bit of homework on streetview. I tend to look on google earth, see where the campers are, zoom in then go on streetview and read the parking restrictions, found some excellent overnight spots this way.
