Quoted:
Yeah, I've seen and shot against quite a few. The Lee Enfield was the mainstay of British target shooting for years, hence many were altered for better performance. One establishment in particular, Fulton's of Bisley, specialised in improving them and to this day you can find many stamped "Fulton's Regulated".

I visit Fulton's quite regularly, including yesterday to sort out a re-barrel for a P14. Not sure if they still offer it, but I would assume so. They aren't always to be trusted with gunsmithing and a lot of negative stories exist, but the older regulated Enfields tend to perform very well and a modern one probably would, too.

Quite a few of these rifles had some form of target sights available and those are usually quite helpful, if rather expensive to source. A lot of the competitive side of things wouldn't allow them in a regular class, but for general range usage, they are a nice buy, particularly for rifles with poor sights like those fitted to the SMLE.

I have seen some K98s which were modified, but not often. Something like a Long Branch No.4 Mk I* would probably be a good place to start, those having an excellent reputation for accuracy here, alongside British made Mk 2s and Mk Is. The Mk I was reputedly the most accurate Enfield.