When’s the interview?
Presumably, they’re closed for the Easter break at the moment so why not telephone and ask them what sort of things they will be assessing when they re-open.
If you’ve already completed level 2, you should be fine.
Colleges need students in order to fund their courses so they’re only going to turn you away if it looks like you’d be unable to benefit from attending the course. They’re not expecting you to be at level 3 standard already, after all.
Just relax and try to enjoy the experience and maybe think about what questions you might like to ask them about the course. Ask if they have any optional units, for instance.