Passed my PPL skills test a couple of weeks ago.
During the planning stage was asked to demonstrate that W&B was within limits and asked if the runway where we would do the various approaches was long enough for our aircraft and the days weather conditions.
At the end of the flight there were various general aircraft questions such as type of flaps fitted, which of 2 specified instruments would be affected by loss of static pressure, etc.
On such technical issues as above I would suggest revising things you need to know in the air such as what is affected by loss of pitot/static pressure and vaccum, what the symptoms are and how to correct. You can't look such things up in the PoH when you're flying.
Anything you feel rusty on revise, if it's flying ask your instructor to take you through them. Try to get your response to emergencies/unusual attitudes as an automatic reaction, bit like changing gear in a car.
As others have said, the examiner is looking to make sure you can fly safely, make safe decisions, not infringe airspace and talk to ATC correctly, he is not looking for perfection. He will do all he can to make you feel relaxed and if you can do that you should be fine.
If your FI thinks you are ready then you are but you need to be confident as well so if you feel a few more hours training will help say so.
Good luck
