Can anyone tell me, on what level your english grammar should be before enrolling on the CELTA course.

I am a native english speaker but my knowledge of grammar is quite basic, do you think I should enrol on a few courses first? Do you know any good ones?

Also, is the CELTA course extremely difficult? I came across a forum of people who failed the course and were quite negative about the whole experience. I would love to hear anyone with postive experiences.

I look forward to your responses.

Yvonne