By the time Pz I, II, or III German tanks got to Kingstanding they'd have gone through 3 sets of tracks and given the time and logistics involved, England south of the Wash & Mersey would've been knackered. The wild Welsh Woolies, the Scots and possibly parts of northern England might have lasted a bit longer. The person(s) who ordered tank traps for brum was obviously a nutcase or a 5th columnist as it was money, time and materiel down the drain.
As for putting a bren in a ready made Stuka target, Dad's Army would've made better of that gun, and the Stuka wouldn't have found it, as it would've been mobile. Ask any bren gunner, like Bannion when he comes back.