Update:

So, I've just re-strung my Gibson USA Les Paul Studio guitar up with my usual Elixir 46-10 gauge strings, and it looks like I've got the nut height, and consequently the 1st-fret action, well and truly nailed, fretting strings just behind the first fret feels good, I don't seem to be getting any fret-buzzing at all on the first fret either, all I need to do is get the 12th-fret action correct and then I'll be happy with it, oh yeah, I just did a quick play through my Marshall amp's clean, overdrive, and boosted-overdrive channels and the guitar is sounding pretty nice and lively so far too.