Hello dear
If no body replied then let me give a chance .Although I am not a qualifier , yet I am senior in respect that I happened to take the exam once
Coming to your query , Past 20 year papers plus Kashmir's Book would suffice if you prepare it throughly.More important thing is that you cover the syllabus first,then all the peripheral concepts that are not explicitly mentioned in the syllabus.For example,while preparing the Solar system you should not restrict yourself to the eight planets only.study Nebula, Constellations etc.Important thing is anticipation and smartness.You can get solved past papers from the market.with all this you can make a difference.
Best of Luck.....