I own two big nikkos, one mk2, rangerfind well and repeating every time in the same point, but the gaps between 45m and 50m is very small. The other nikko is a mk3, rangerfind well, the gaps are wider and has slighly better glass, but is more affected with changes of temperatures.
I own a S&B FT, is my best scope, excellent glass and cuality, rangerfind very well, but is afected by temperatures changes. Ive tried a S&B PM2 of a friend, very similar to the FT model in glass quality, the gaps are smaller but not bad. But suffer the same problem of the FT model with the temperatures. Maybe in UK, with less extreme temps will work better than FT model.
Ive tried two sightrons, one mildot and one lrmoa, the glass is slightly better than nikkos, but the rangerfind is very similar to my nikko mk2, the gaps near 50m are small, very small. and the wide of view is more narrow than big nikkos.
Ive tried some nikkos of friends and i have to say that every scope is different, different in cuality of lens and rangerfind, my word is that there are good and poor nikkos. If you find a good nikko, it will better for the money than the sightron, with similar glass and better rangerfind.
Ive tried some leupolds comps 35x and 45x. The 35x has very good glass but you have to know how rangerfind with it. The 45x is a bit dark but rangerfind better. Maybe the 40x is the best leupold for FT.