"I can't call him - ever. This stems from his separation and the fact that he might be with his daughter. This is wrong isn't it?"
It stems from him being with somebody else and afraid she'll catch him talking to you. If not his wife, another GF.
"He doesn't respond to my messages when he is with his kids. I'm OK with this normally but tonight my car broke down and I'm on my own in the cold and dark. He hasn't even messaged to see if I'm ok. (and I'm not - I'm crying on my own)"
You should not be okay with such rudeness ever.
"He says that he feels love but he can't say that he;s in love with me because he wants things to settle down at home first (he separated last year and we have been seeing each other for over a year now)"
He can't say some words because things need to "settle down" at home? OP, come on. He is obviously still hung up on his wife.
"He never arranges to see me until the last minute - he says that this is because he has to see what the family are doing - but he seems to commit time to see his friends OK"
Are you okay with being an afterthought and a convenience when he has nothing else to do?
"I don't want anything but he never even thinks to buy me anything, even a bottle of wine when hes coming round for dinner."
Cheap, selfish prick.
Dump dump dump for all the reasons above and undoubtedly many more. He's using you and he's a greasy liar. I'm really sorry, but you do need to face this.