I think you need to bear in mind that folklore about faeries, elves, boggarts, brownies, knockers, hobs and Pucks and a whole array of other such beings exists all over the British Isles and Ireland, including the historically English-speaking parts. One area where there is a rich treasury of folklore is Lancashire, with the marsh boggarts, and Wessex is also rich in stories about piskies and fairies and Kent has its stories about fairy sparks. I don’t think you can say it was “English culture” at all since “English culture” is rich in folklore concerning these beings. The Christian church(es) throughout the British Isles and Ireland was/were obviously not too keen on the ways of the country folk, but they certainly didn’t try to tell people that these beings didn’t exist at all and throughout the medieval period, obviously a Christian period, varying explanations for these beings was given – but their existence was not denied. It’s interesting to note that Robert Kirk, who wrote The Secret Commonwealth (1692), was a minister of the church.
It is only with the so-called Age of Enlightenment, science, rationalism and industrialisation that this folklore began to wane. Increasing urbanisation and detachment from nature and the wild, alongside puritanical/17th – 18th century Protestant attitudes towards anything considered medieval and superstitious, also contributed to this no doubt.
Another thing that ought to be borne in mind is that in “genuine” or traditional folklore, there were numerous different kinds of entities, some good, some bad and some ambivalent and they usually have little in common with the faeries of popular imagination today, which are more of a Victorian invention.
The dynastic politics and warfare of various royal houses in the British Isles is complex. The great irony is that the Tudor dynasty – a Welsh family, actually dealt a severe blow to the Welsh language and brought Cornish culture to its knees. There was never a time when all of Scotland spoke Scots Gaelic, the south-eastern parts were historically Northumbrian-English speaking and the current Scots language/dialect is far more similar to Middle and Old English than probably any other form of English currently spoken elsewhere. In the Shetlands and Orkney Islands, a dialect of Norse, Norn, was spoken right up to the 19th century and the dialects still spoken in those islands are rich in terminology from Old Norse. Scots, as opposed to Gaelic, was already becoming the prestige language in Scotland during the 14th century and by the time of James I/VI, was the language of the influential court and its power base in Edinburgh. During this period, English came to be known as Scots and Gaelic as Irish or Erse in Scotland – marking the changes in society. You also need to bear in mind that for about three hundred and fifty years, the kings of England didn’t speak English as a first language, they spoke French and it was only in the late 14th and early 15th centuries that English began to be used at court. To this day, experts in Norman-French need to be consulted when looking at ancient laws and the statute that allowed English to be used in court (1362) was actually written in … French!