As Nick said, Ase mods can use the BoreLock muzzle brake. I have this combo and bought it complete as such; muzzle brake and moderator in a package.
A lot more American made moderators attach to muzzle brakes. As far as I know, only the Ase, Accuracy International and certain models of MAE moderator can be fitted to a brake.
Is the consensus that in the UK/Europe people would tend to use one or the other? As in, being happy to completely unscrew a brake to put a mod on?