Years and years ago, my very first pistol was an Enfield No.2 Mk.Iólike yours, but the kind with a hammer spur and a full-cock notch.
I also had the Parker-Hale conversion to .22LR, which consisted of a cylinder and a barrel liner. The barrel liner had a supplementary rear sight at the breech end, and a retaining nut at the muzzle. The cylinder's chambers were bored at an angle to the barrel, so that the CF firing pin would hit the rim of the .22 cartridges. Even though the bullets took a (approximately) 10į turn, it was a pretty accurate outfit.