They are for free and non doctrinal .... you can't make them better or as good as ML20 / LeFH. Since they don't cost resources and don't take popcap.
they are hardly "free" when they require your tommies to get within grenade distance and spend 45 mu to throw a smoke.
To answer the OP. It's a good concept and useful in certain situation. Unfortunately it still leaves the brits without a non-doctrine mobile artillery. The sexton isn't that good either.