Motorway service stations - 2 hour parking limit at most of them, which is difficult for them to actually enforce via implied contract in civil law, but why bother with the hassle?
Industrial/business parks - Good at weekends when not busy, but watch out for controlled parking signs, caveat as above
Car parks of churches/pubs/schools/universities/airports - If clearly no parking restrictions. plenty of space, and not obstructing bone fide users then fine. Pubs you are usually obliged morally or by condition to eat and drink there. Schools I would not do (nanny state/predator/child abuse hysteria etc). Universities often have parking congestion and restriction, see point 1. Airports, forget it, unless you want to pay rip-off parking charges, you may as well use a campsite.
Ports - Never tried it, but noisy if you are talking about docks...find a quiet place in town
Quiet cul-de-sac's/crescents in residential neighbourhoods - The best so far but not directly in front of some stupid NIMBY's house. Far better to find a place outside someone's long, high, back garden fence or wall. Exception... if the street is commonly chock full of parking and you adopt a stealth approach, but if it's usually parked nose to tail, then it's not "quiet".
Other places - The best urban place is on a quiet tree lined street outside a long fence or wall that is the boundary to the grounds of some large school, residential home, park, public buildings etc etc. There is nobody to complain or overlook you, just the trees and grass, and in any case there is a fence or trees to shield you. In this instance a school is OK as you are not actually in the school car park, just on a street near it. The best type of schools are private ones with extensive grounds. This type of location is infinitely better than a supermarket car park where you may be approached, or need to keep on asking if it is OK, or feel obliged to patronise the venue, be it a shop or a pub.
