I think for english it's worth getting an actual english teacher (even someone who has been an assessor in the past/is an assessor) as opposed to a student even if they are HD'ing their arts course/got fantastic results in english at school, just because a teacher would know exactly what is wanted/how to phrase it/etc.
They would basically be telling you ways to improve your writing - lack of quotes, not enough fluency, too verbose, whatever as well as give you some insights into your texts.
Whether they help, I don't know, though I'd say mine did. English is a hard subject to tutor...