Neither the HKS S&W M25-2 (.45 Auto Rim) or the M25-5 (.45 LC) speed loaders will fit .455 Webley. You can sort of wiggle in the mk1 cases (or at least these Dominion .455 Colts) into the .45 Auto Rim version, but the necessary ejection procedure (the negative end of a AAA battery) is antithetical to the concept of a "speed loader." And my well-loved Fiocchi Mk2's...fuggedaboudit.
This makes me a sad panda. Back to practicing the time-honored "pocketful of loose cartridges" reloading method. And if anyone reads this, it may just save them $13 trying out speedloaders.