I've never seen an 18-inch barrelled .45LC Ruger revolver in this country or heard of any being imported. They made about 100 in .44 Magnum and another run (don't know how many) in .357 Magnum. Also about 200 Ruger Mini-14s were imported as straight-pull rifles and a few dozen Ruger Mini-30s. This is the ad:
Most of them were converted by Sabre Defence, by welding a rod onto the grip extending backwards and the barrel was cut down to 12 inches.
Under GB law, the minimum OAL for a firearm is 60cm and the minimum barrel length is 30cm, so they are legal.
Viking Arms wanted Ruger to make them that way from the factory, but they couldn't, as they would be classed as an "Any Other Weapon" under the NFA.
I think basically Bill Ruger took pity on us, because as soon as he died, Ruger lost interest in selling them.
Only Taurus makes them now.
I would have thought one in .45LC would be a pretty rare bird, might be collectable. Like I said, I haven't come across any here.