hun i know how u feel, my instructor used to ring me and cancel lessons cos he was juggling so many students, and it made me feel like i wasnt his priority... the oil water etc is really easy, and wont take 2 mins to learn, even my sister can do it and thats a miracle hehe...
take the test anyway. i honestly feel even if u dont pass the experience of a test environement is the best lesson ur going to learn about driving, and give u so much confidance if you do fail... big fingers crossed u pass... but honestly, its not the end of the world if you dont cos u will have time to prepare more after. but try keep calm and focus on the test
really good luck!!
katie x