I assume that it's a public (rather than private) road.
It's an offence, under Section of 137 of the Highways Act 1980 to wilfully obstruct any highway.
More specifically, it's also an offence, under Regulation 103 of the Road Vehicles (Construction and Use) Regulations 1986 for anyone to cause or permit a vehicle to stand on a road so as to cause an unnecessary obstruction.
Speak to your local community constable. He (or she) will probably be happy to 'have a quiet word' with your neighbours.
Chris