the hw iron sights are some of the best in the world, if you have to have an optic i would recommend a red dot rather than a scope as the recoil on the 45 can be a bit vicious, with a scope any thing over 2.5 mag and the shaking is too much and the extra weight makes a big difference (even though you held the scope on its own and it weighs next to nothing) on a reasonably heavy pistol at arms length it feels like you've added a 5kg weight especially during a prolonged shoot, i know you used to be able to get a shoulder stock for the hw45
personally i think .22 pistols are not the best idea (unless for point blank range "humane dispatch") before anyone starts yelling, i am of the .177 is best camp, but in a pistol (sub 6 foot pounds) .22 just has not got the speed to keep a reasonable trajectory, with my 45 (.177 running at about 4.5 - 5 foot pounds) i can get decent groups at 20m (with a bit of practice) but others with a .22 45 have problems, at 10 m the groupings become lot better and they say a light weight pellet gives best results