double mortars or rush a FHT
Never spend manpower on normal mortars vs emplacements. Flame HT might be nice if there is no Bofors and no AT gun, otherwise pretty useless. Maybe if you get in under 5min min mark. Best counter is probably spotting scopes + pak, or save for LeFh with Ostheer recoup losses. The Counterbarage is a timed ability now that cost ammo, it might decrew the LeFh once, but it will not keep up.
Other option (and the best one imo) is secure flanks get some tanks > rush base. with 3 P4 you can kill brit base in a min.