Pink Cloud: Yes. Please go and find another instructor, be it from your friends or colleagues at work.
Ur current instructor sounds highly suspicious. He should not be having so much problem booking a circuit slot for you. In fact, for my 2 instructors, they did not have any problem booking at all. 64 bucks for 2 hrs is pretty steep. Usually for private manual driving, it should range between $24-26 per hour.
On the actual test date, try as much as possible to do things to make yourself calm. From my 1st attempt test, I realised that it was a nerve-wrecking experience waiting in the "classroom" for my TP to pick me. Thus, for my 2nd attempt test,I went in with a non-chalant attitude and brought in my DS Lite game. It somehow helped me remain calm throughout the test. I guess, when u remain calm, it shows the TP that u are confident and in control of the vehicle. All the best!!