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.