As stated elsewhere, my biggest problem with British Emplacements is that you can't deconstruct them, so either you end up with something near the front line that is extremely vulnerable (and end up just throwing away resources when it is destroyed) or you end up with something safer but no longer able to participate in the fighting (and thus end up throwing away population).
That's the tradeoff, in'it? Build it forward so that it can do maximum damage, but it's also vulnerable if you get forced off the field. (If only brits had some sort of forward reinforcement point they could build?...) Build it too far back and it does less damage, but this isn't necessarily a bad thing. A mortar pit or bofors can defend your cutoffs and other points that are behind your lines.
Personally, I've found that a good mortar pit is incredibly useful. Bofors is trickier to use, but in a good spot and it can help a ton. It's not as durable as say a panzer command, but if you put a crew inside it can shoot a lot further and has brace to somewhat protect itself. The barrage is also excellent for haranguing opponents from afar. 17lber is a lot trickier, but works well in big open areas like the center of langreskaya and it has enough range that you can use it to punish your opponent for pushing too deep with his vehicles.