Your current scores should see you pass the Use of English paper. I would spend as much time as I could reading different texts and looking at verb + dependent prepositions etc. This should help you with the multiple choice gap fill exercise. Also look at confusing words (try Why are words so confusing? | IELTS ONLY).
Don't ---- repeat don't ----- do too many past papers. As long as you understand the exam and what is expected of you, you are better spending your time learning English. Doing past papers will only show you what you get wrong (and right) in those papers. If you do a past paper, make sure you look up why answers are wrong!!
Hope this helps.