Well done G-LOST - you must have followed the three basic rules for passing an IR test:
1) Stay focused - you must concentrate all your efforts on passing the test. Changing flying schools, aircraft or examiners rarely helps - it's generally up to you.
2) Spend more time studying on the ground than flying. As they say, every hour in the air should be preceeded by 2 hours on the ground.
3) Don't let the pressure get to you. Your examiner can play a big part in this. Some help you feel at ease, whereas some don't. At the end of the day, don't worry too much about staying within the specified tolerances. The examiner is more interested in the fact that you can competently handle the flight - prove that to him and you should pass.
Proof that the IR is passable first time!