If 100 meter shots will be long shots for you, why did you pick the .300 H&H, which is a purely long range cartridge? For the shorter ranges the 220 grain bullet would obviously be the choice, but a 220 grain projectile in, say, a 9.3X74R would clearly be a better one. Although the 285 grain load is certainly the most popular for the 9.3X74R, RWS and Norma offer several loads with bullet weights ranging from 225 to 247 grains, which would be in the same recoil category as the .300 H&H with the 220 grain bullet. If Purdey turn up their nose at a metric caliber, then the .375 H&H Flanged would be the next best alternative.

I am assuming that you are ordering a rifle built. If you are dealing with a pre-existing rifle in caliber .300 H&H Flanged, then by all means, the 220 grain bullet. The next owner can have the rifle regulated to suit himself.