Zulu remember this piece of advice for the RBI part:
THE RBI NEEDLE ALWAYS POINTS TO THE BEACON. Thus you have to rotate that instrument round in your head to fit the situation. The other 2 instruments, the compass & artificial horizon are self explanatory and will help you fix your position in space to coincide with one of the a/c on screen.
I remember when i took my test a couple of weeks ago i got to this point and i totally freaked out! After regaining my composure and remembering the OAA teams guidance to go back and read the instructions as many times as i liked it just clicked (after reading it 3 times) and well the rest is history and i sailed through to pass the OAA skills assssment.
The test is not biased. Don't worry relax and go do it again. A friend of mine failed 2 years ago and he resat and passed and now flies 737's for BA!
good luck.