They have a smoke nade that calls 2 howies from their base with no doctrine. Lack of non doctrine indirect fire?
They do have it, but it's a waste of munitions. The only time it is guaranteed to do any damage at all is on static positions, and we're not talking "getting slammed by 152s from last patch" level damage. I've seen the base howitzers cast on an mg that didn't even reposition and come out unscathed. The amount of time it gives them to retreat is positively huge, so they could actually increase the firepower of these barrages substantially but still have them be basically ineffective except to force people to reposition their units in response. It's not really "non-doctrinal artillery", it's more like a crappy satchel charge.
I think Brits can be mobile just nobody knows wtf they're doing with them yet so they just play defensively with multiple Vickers etc. The fact that Vickers are bugged with their range could possibly have something to do with that(just maybe lol). I could see an early 5 man upgrade with LMG's and/or upgraded Bren Carrier being very mobile and powerful. It's also early in their life span, VERY early. Tommies will be tweaked, things will change. But I think it's much better to adjust tommies to scale than over-do emplacements.
Mortar pit should be pretty resilient vs other mortars but very weak vs fire and shreks and very weak during construction to small arms in general. All other emplacements should be vulnerable to mortars and indirect fire. This is how it was in vCOH and honestly I can't see a balanced alternative. This brace nonsense has got to get revamped or go.
Brits can be played mobile, but it's broadly ineffective in the early-mid game. You can't compete in numerical terms and have no real way to dislodge enemy MG strongpoints until you get the (about to be significantly nerfed) Universal Carrier Wasp upgrade, which explodes when a stiff breeze is thrown its way. You can hold land, but then when the enemy responds to your MGs and infantry positions with indirect fire, the only two responses are try to rush their indirect, or build a mortar pit. But their indirect is itself kind of a hard counter to yours, and your own indirect is needed to counter their Mgs. Which it can't do while also getting shelled by their indirect. It's a real mess, balance wise. Sometimes you can get it to work but it's not reliable. Every game is more or less stalling for tanks, because when you get to T3 you legitimately do have what it takes to get a hard hitting fast moving army.