But when my opponent sent me back turn 0 and i went to the deployement screen, I found out my Brits had nowhere to deploy !

So i did some testing and it seems that the set-up lines edited in the deploy screen for a given map in the editor are used for random battle using the map (but that objectives hexes are not)
I think it is in fact a good feature since I don't like the random front-lines of random maps (too close to each other in all battles and not enough depth for defenders), but it would be nice to have a section in the manual about it and maybe some on-screen warning when you start a battle.
And as far as my PBEM battle is concerned, I have obviously to restart it. The only good news is that we had settled on small budgets...
------------------
always to the last man