Webwise you could do worse than armoured acorn H:
Armoured_Acorn_British_Markings Armoured_acorn
Or is it more the tactical markings you're after?
If so, those Histoire Collections 'British Soldier in Normandy' are pretty clear and go into some depth (though only for '44 onwards).
BT White's 'British Tank Markings' is pretty good, if somewhat long in the tooth and fetching slightly silly prices for a slim volume.