Hi Simon,
I have only used a couple o/b mods in the time ive been shooting both foxing and deer stalking,
I did use Wildcat Evolution mods recommend them well made british engineered design, strippable mod, good sound reduction,
competitively priced and cheaper to buy than other reflex mods,
I've gone to using Stalon mods with a W145 on my 243 the old model, not strippable compared to the evo, again well made product
my guide who I go to for roe stalking in yorkshire thought it was good,
They have a different model out now called the X108/X145 which is a lighter and slimmer design, you can still get hold of the W series from some rfds.
The other I can recommend not from owning it myself but when I started out deer stalking, my deer guide up in scotland had a dpt 6mm ob mod with
a couple of extra baffles added on the estates rifle that i used,
That was a really good sound mod strippable like the evo but customisable with the option to add extra and stainless baffles too,
I dont think you could go wrong with any of the above really