This is a bit longwinded but might prove useful:
"5.3 Nuisance and trespass
Interfering with a right of way is a civil wrong, namely a nuisance. As
Barsby states, a person whose land has the benefit of a right of way
may take action against any person interfering with his right, whether
the owner of the road or a person who also enjoys a right of way, or
someone unconnected with the road. For example, a right to take
action might arise if the parking of cars in a narrow private road
persistently interfered with the exercise of a right of way, such as in the case of Horne and Horne v. Ball [1995] CLY 1841 in which the court had to deal with deliberate obstruction, accompanied by verbal abuse over a long period.27
In the case of trespass, i.e. going onto land unlawfully or exceeding the scope of one’s authority to go on to land, Barsby states that:
Any person in possession of land can take legal action for
trespass, whether or not they are the owner of the land, since the
policy of the law is to protect a person in that position against
anyone other than the true owner of the land. This is particularly
important where the ownership of a private road is unknown…28
5.4 Parking
Generally, there is no general right to park in a private or unadopted
road except for the owner of the road. In practice parking may be
permitted or tolerated by the owner (in which case there is a licence to
park) and in some cases a legal right may have been granted by the
owner.29 As Barsby explains, parking in a private or unadopted road
without permission or a legal right to do so is trespassing, and is a civil wrong for which redress can be obtained. The wrong is done to the owner of the road or, if different, the person in possession of it:
That person can bring legal proceedings to obtain compensation,
though the amount of harm done would typically be small and
the compensation therefore very modest. The owner is also
entitled to insist that trespassing ceases, and could if need be
obtain an injunction against the person concerned.30
Whether or not someone is trespassing by parking in a private road, if
they obstruct the road and so interfere with its use by those with private rights of way, a different civil wrong (nuisance) is committed. In this case, the civil wrong would be against the person whose land has the benefit of the right of way, probably the owners of the properties. The same would also be true if a parked car obstructed access to a private road. In a case of nuisance the civil courts may grant compensation and other remedies, such as an injunction.31
In some particular circumstances a criminal offence may be committed.
Under section 34 of the Road Traffic Act 1988, as amended, it is an
offence to drive a motor vehicle without authority on land which is not
a road (i.e. a road that is not a highway, or to which the public has
access) save where a person goes no further than 15 yards from a public road, and does so in order to park. On a private road to which the public does not have access, drivers who come onto the road without authority are committing an offence unless they do so in order to park and go no further than 15 yards from a public road. If they park within 15 yards of a public road, they will merely be trespassing, not committing an offence.
Anyone facing parking problems on private roads should consult a legal professional. Information on sources of legal assistance can be
found in HC Library briefing paper CBP 3207.
Commons Library Briefing, 10 April 2018"
It's part of a pdf download that you can get by googling Private Roads in the UK - it's the Briefing Paper dated April 2018 for the Govt. I can't give you the link because it keeps linking to my name!!