I don't have a definitive answer but this may help: Open Street Map is a free but incomplete mapping of UK roads. They currently have roughly 250,000 "ways" where a way represents a section of road as a directed sequence of points. Some roads need more than one "way" to represent their shape e.g. a "T" shape needs 2 ways whereas an "L" shape only needs one.
397,403 km / 246,988 miles (Ordanance Suvey Mapping, 2006)
About 21.3 miles by road.
The distance between Cardiff, UK and Abergavenny, UK is about 32.1 road miles.
The distance between Holyhead UK and Swansea UK is about 170 road miles.
About 85 miles by road.
London to Paris by road (and ferry!) is about 290 miles.
The driving distance from Alicante to Manchester is 1,471 road miles.
The driving distance is approximately 11.4 road miles.
The driving distance from Durham, UK to Leicester, UK is 172.05mi / 276.88km
a lot Or 160 miles by road and ferry according to our friends at google maps
Road miles between London UK to he city of Holyhead Wales UK
The driving distance is about 20.6 road miles.
There are roughly 4700 miles between UK and Pakistan by road.