There are some which allow parking but not camping (often defined as dwelling, sleeping and/or eating) overnight. Listed below are links to those places where, according to the information received, overnight camping is allowed (though this may not be in all car parks in the area).
Overnight camping may be allowed in other areas but as the information gathered is not explicit it was decided to err on the side of caution.
It should always be remembered that the situation can change so best to check signs before settling down for the night just in case.
Also check out the Stopover information at
UKMotorhomes.net as it may well be more up to date.