Thanks for your comments guys. I'm building walls for two reasons- the first one is that it is my first PBEM and I don't realy know what I'm doing
the second reason is that cartouche Bee is playing 1.21f while I'm on 1.27f- the wall bug has been sorted for 1.27 but not 1.21 so if CB attacks my settlements when they become cities the walls will act as massive force multipliers so I am hoping that he will launch the first attack and his military will hopefully be broken upon my walls and then I can counter strike.
My policy towards CB at the moment is simply to shoe horn him into his peninsula while I slowly expand into the available area building barracks, walls and defensive troops primarily with the occasional horseman thrown in. Normally on an SP game I would have cut down the game forest and would have expanded much more rapidily but it would be too easy for the opposing player to do warrior-swordsman mass upgrade and burst my bubble in my view.