This is just further to Penny's point that the problem with Britain is that the landscape is very busy, full of features which might be significant, bearing in mind kat's comment on Watkin's theory that ancient sites around Britain had actually been constructed or formed giving alignments between and across the inhabited landscape of Britain. The sites mentioned include Stone Circles, Standing Stones, Long Barrows, Cairns, Burial Mounds and Churches.
That's a heck of a lot of archaeological sites, as Penny indicates. I'd like to know which sites get included and which don't. Why do some sit on these "ley lines" and others don't? Or do they all - and there are thousands and thousands - and that's only the ones we can see above ground. What factors include one site and exclude the next? How thick are these lines - a couple of metres wide, a couple of miles wide? How exact are the points fitted to these lines? How discrimating do you have to be to get the results you want?

If we're referring to landmarks above ground - in particular elevated structures (e.g. church with spire, mounds etc) the eye is likely to connect these, as Wolfgang talks about when he mentions pattern recognition. Picking out ley lines seems as difficult as picking out lines of postholes and trying to find structures on a post-excavation plan of an archaeological dig. Bloody tricky - and open to interpretation unless you have a wide range of supporting evidence.