I think that if the damage to his car was at the side, he was cutting across your path. Even if he was indicating, why did he cut across you. Under either scenario (indicating or not) he failed to look behind.
As far as your excess is concerned, does your insurance have the option to recover it.
I think your chances are good, especially with your witness. Sadly, even if you win, your insurer may still put your basic premium up because their stats show that accident victims are more likely than average to be involved in an accident even if it is not your fault. Disgusting, I know.