https://en.wikipedia.org/wiki/Category:Standing_Anglo-Saxon_...
Looking through the list, it seems that in the Anglo-Saxon portions of all those buildings, any arches were relatively narrow and crudely fashioned compared to subsequent Norman style. So I guess there was quite a gap in sophistication of architectural knowledge between Britain and the Continent in the 11th century.
From the book:
...within fifty years of 1066 every English cathedral church and most major abbeys had been razed to the ground, and rebuilt in a new continental style, known to architects as 'Romanesque'. (p. 10)
...No English cathedral retains any masonry above ground which dates from before the Conquest. (p. 11)
...Old England, in an architectural sense, had been eradicated. (p. 12)
Building anything is quite complicated. Surveying, logistics, material sciences, geotechnics and more.
The old Greeks kicked off some of the modern forms of civilisation (eg demos kratos) but the old Romans ran with it, big style and added to it. The old Romans invented concrete and a modern Civ Eng appreciates the stuff and we have made a few changes to it in the form of additives.
For starters concrete is a chemical reaction, exothermic, and will work underwater.
The Romans also gave us the Roman arch - circular based. They seemed to have lacked a formal analysis of other geometries for arches or even considered them. The "Norman" arch has a point of inflection and can usefully narrow the space required.
Building anything is sodding complicated - try it!