The only Louis L'Amour I've ever read wasn't even really a western and was instead science it's fiction (or maybe fantasy, depending on how you define the two) called The Haunted Mesa that features a portal between the modern world and a world ruled by the Anasazi. I read it a long time ago, but I recall liking it well enough. I might even have to revisit that, come to think of it.
It's the only Louis L'Amour book I have read, got on my Kindle. The hero takes a while to 'cross over', but I like it.
As a kid, I read some of the Edge books by George Gilman, was surprised to find out a few years ago that he was a Brit.
Another British writer of westerns was JT Edson, controversial because he rewrote reason behind the Civil War, making it more about independant states unifying for mutual protection and trade and seceding from the Union because of 'interference from Washington in independant states internal affairs' rather than slavery, which he preached was used by left wing Liberals to recruit 'ignorant northerners' to become 'modern day crusaders' against the cruel oppressing southern states. This was only background detail in what was, I think, standard western adventures.
His mainstream heroes were ex-Captain Dusty Fog, Mark Counter, the Ysabel Kid, later joined by Doc Leroy and Waco, although were others. My favourite character, by far, was the Comanche half-breed Loncey Dalton Ysabel, aka, the Ysabel Kid, mostly because he was the least 'moral' of his all-gooder stable of heroes.
Sadly, his death probably means we will never see the Old Age Pensioners Dusty Fog, Mark Counter and the Ysabel Kid's Last Stand in Africa...
I have read a couple of 'Sudden' books by Oliver Strange (another Englishman!), a Six Gun Samurai book, forgotten author's name and a couple others.
Mostly I was reading science fiction, fantasy or horror (mostly Perry Rhodan and Doctor Who novelisations, Michael Moorcock and James Herbert and Guy N Smith!).