It's a wonder the well was never shut down (especially as, apparently, the Gunpowder Plotters went there); it's not that far from the English border and hardly in what you'd call remote moorlands. It did have some powerful patrons at various points. Margaret Beaufort, Henry VII's mother, was its most important late 15th-century patron. Two centuries later, James II and his second wife made a pilgrimage in 1687, hoping for the saint's intervention to give them an heir. And we know the trouble that led to in 1688.* The well was ransacked by anti-catholic rioters after the Revolution, but was going strong again in the eighteenth century - more as a bathing 'spa' than a site of religious pilgrimage.
The Cistercian Way: Holywell
St Winefride's Well
The BBC recounts the well-known legend: a local chieftain beheaded the maiden Winefride after she rejected him. A spring rose from the point where her head fell (before it was miraculously restored to its owner's neck, which the BBC doesn't mention). And "the stones surrounding the fountain were stained forever with her blood, and the blood falling in the water coloured also the moss that grows there and which has the perfume of frankincense, though some say of violets." The BBC also doesn't go on to mention the story Celia Fiennes told about the moss, the locals and the pilgrims:
I saw abundance of the devout papists on their knees all round the well; poor people are deluded into an ignorant blind zeal and to be pitied by us that have the advantage of knowing better and ought to be better. There is some small stones of a reddish colour in the well said to be some of St Winifred's blood also, which the poor people take out and bring to the strangers for curiosity and relicts, and also moss about the banks full of great virtue for every thing - but its a certain game ['gaine' in my text] to the poor people, every one gives them something for bringing them moss and the stones.
This online extract doesn't add the postscript (and I don't have my notes here to quote it, unfortunately): Celia notes that she was told that the local poor didn't simply go down into the well to fetch moss for the pilgrims: at night they took moss taken from elsewhere and stuck it onto the sides of the well in order to meet demand!
BTW, if Winifred sounds familiar to crime fiction readers, she is the same saint who is so dear to Cadfael in Ellis Peters' A morbid taste for bones.
*For anyone reading this who doesn't know much seventeenth-century history, it was the birth of a male heir and hence the prospect of a Catholic succession that sparked off the 'Glorious Revolution'. This heir was James, 'The Old Pretender'.)