Hello,
I subscribed to "scottsenglish.com", I paid USD49 for one months unlimited access which gives online tuition and lots of hints and most importantly practice tests. I found it very helpful, I think the key is to practice under the time constraint as that's what causes people the most difficulty. I have heard that if you fall short by half a mark you can have your paper remarked but am not sure how you would go about this. Hopefully another member will be able to tell you how to request a remark.
Good Luck !