If you see your against a brit player, just play to expect an AEC and get a PaK at ASAP and dont skip tech.. its pretty simple. If he over extends his AEC faust and its dead, bye bye wasted fuel and longer wait till cromwell. This is the same as how brits have to rush AT gun to counter 7 min Luchs.
It's not like brits will have much map control anyway, if they rush AEC the most their army will be is 2 IS and an Vickers... don't expect them to do much
AEC can come out at around 6:00 (with equal map control), on large maps, you physically can't have a PAK out on time, and in a decent position. BEST case, it's just rolled onto the map when the AEC starts wrecking everything. Also, you'd be amazed how well 2 squads and a vickers can do on some of the narrow maps (Rails and Metal, Kharkov, even ecliptic if they start south. And that's if both go AEC, usually only 1 of them rushes it, the other goes inf heavy. Remember that the brit infantry cover bonus is a pretty hefty force multiplier.