Well I can't comment on a Varmint as I have an American WMR and I have only been able to try four different bullets in it so far:-
Winchester - Super X 34 grn Hollow point "Varmint load"
Winchester - Super X 40 grn JHP
Federal - Classic 50 grn JHP
Remington - Premier 33 grin V Max (ballistic tip)
We have trouble getting hold of a big variety of ammo up here in the Scottish Highlands. The dealers usually just keep in stock what sells the best and in WMR that tends to be Winchester. There is more choice in lr. The Remington and Federal were ordered in by my gunshop especially for me.
As far as they shoot, I have only hunted with the Winchesters and the remingtons which resulted in clean kills on rabbits, approx 120 yards, you have to hit them in the head or they are returned to kit form. I got a Fox with the Remington about 75 yards, clean kill, heart/lung shot dropped where it was. I think I would feel confident at twice that distance but I would need to be able to be sure of placing the shot accurately. Which would not be a problem with any of the ammunition above, they all group good enough for that and the gun likes them all. I want to try and get some CCI Maxi Mag TNT's I hear nothing but good things about them.
I am also familiar with those Diamonds was on about that his wife uses, nice but expensive.
Cheers
JohnB