I take the point about church architecture, but all are orientated east-west, so are similar, and have been for centuries. Orientation seems to be popular in Neolithic/Bronze Age burials.

What are the odds of a belief system, both spiritual and architectural, being very similar throughout Britain and Ireland during the Neolithic and Bronze Ages? Add to that the hardship involved in travelling just 50 miles and you have to wonder about the apparently similar belief systems.

Surely, if similar belief systems existed, then you would expect similar architectural edifices.

The fact that these similar edifices exist in Europe is perhaps idicative of early migration patterns.

Interesting fact about Maes Howe is that recent researches found evidence for at least a pre-existant standing stone, so the idea is that Maes Howe was built on the site of an henge. Could it be that the mound was mostly finished before the stone structure was fully under way ? Nah ! Second thought; if a Neolithic 'tourist' took the mound idea from Maes Howe maybe the site was only seen from afar, too sacred to allow just anyone near. So copied only a mound.
If rather than being homologous Maes Howe and Silbury are analogous could it be the lack of decent structures found within the latter is that Silbury Hill too has been built over a pre-existing henge monument, only without any other mods ?