If you take a line from the Merry Maidens to the Hurler's (or King Doniert's stone) to Glastonbury Abbey to Silbury Hill a "Line" if formed; the "St. Michaels Ley Line"
I see the corollary in that if a pattern of megalithic sites form a grid of consequence you could also pinpoint all the pubs in London so that a similar pattern of "Pub Lines" would be formed.
you are already on the right track...
Watson's definition was four points connected with a line, and he gave himself a latitude of 1/4 degrees too, according to Wikipedia.
look at this pic
80 4-point "ley lines" pass through 137 random points.
The sheer amount of places he was able to pick, from churches, hilltops, megalithic sites in England, makes it not very difficult to find alignments.
Lines and points on a map cover wide areas on the ground. With 1:63360 (1-inch-to-the-mile) maps a 1/100-inch (1/4 mm) wide line represents a path over 50 feet (15 m) across. And in travelling across a sheet, an angle of 1/4 degree encompasses something like an additional 600 feet (200 m).
Also, the notion of "energies" flowing along these lines were not something that Watson cared about. At all.
In fact, that was invented by Dion Fortune.
I still do not see a reason to assume (note not "believe") that there are aligned monuments anyhwere, not only in England.