If you've got Mobile Assault I've had a lot of success with Hector's guide for it. It gives a good general grounding in the faction's playstyle and the principles of it are fairly transferable to other commanders too. Bear in mind it's pre-December Balance Patch so the fine details might be slightly off now.
https://www.coh2.org/guides/62518/british-bastards-a-mobile-assault-regiment-guide
The Bren Carrier: the question you need to ask yourself with it is are you getting more use out of it than another Infantry Section or HMG? I see it in high level streams occasionally and I personally find it useful if I'm up against OKW or Assault Grenadiers.
The AEC: It's your most powerful early AT option but delays your first Cromwell. The decision for if you build an AEC is can you deal with enemy light vehicles without it? Hector's guide goes into this decision and your other options in more depth.
The Cromwell: It's a good medium tank, about on par with the Panzer IV which is likely to be its main opponent.
Hammer: You research Hammer when you want the Comet, which is a really good tank that can take on Panthers with proper support. When to stop building Cromwells and unlock the Comet is a call you have to make.
Being snared by Panzerfausts: Your vehicles are faster and have a longer range than infantry with snares so if you stay at range you can avoid them. Keep infantry near your tanks to punish any squads that try to charge the tank.