id go with churchill. should go a little faster but the armour is strong and the gun is powerful and accurate.
I pick the Matilda I as my fave. It's simply so fun to use. Slowly plodding along towards the enemy with the MG firing..... so armoured you're a god!
Churchill is my favourite, just because the feeling of absolute invincibilty against infantry and sometimes other tanks just can't shoot at it fast enough. I remember once I was in a churchill, a tiger came over the hill, I got a shot at it, it shot me and while I was still smoking I survived to pump a round into the tiger that set it off while any other tank would've been blown in the first shot.
Churchill is way too slow for me..
the firefly is just the coolest tank for the brits.