Applying for a College/Sixth Form (A-Levels)

I've just started year 11 and apparently you need to apply for colleges and sixth forms before my GCSE. Is this true? i'm planning on going to a decent college with pretty reasonable requirements (B or above), I've only decided to start revise properly this year which means my grades from year 10 were pretty bad.

Do colleges look at my predicted grades? Or my actual mock exam grades?

I'm pretty confident that I will get good grades since ive started revising now for gcse, but im just ******** it because I'm scared colleges aren't going to accept me because of my predicted and current grades.