Sorry, have to correct:
1d Answer is co-star = Fellow principal;German east = OST Inside car(e) = charge ............so F is your new letter
25d Answer bucko: means bully; cub=youngster, reversed; not sure about OK and lippy & flatten, but it's defo correct.
Complicated ones, and the whole thing is too, but very worthwhile when you get there (you will know the target if not all the characters' names) --- and take a look at the relatively long thread that already exists for further help!