if he doesn't want to give you his car then im 99% sure you're not ready for your test at all. Don't do it. I know this because i had a similar experience, I thought i was ready while my instructor disagreed, turns out i did my test when my instructor thought it was ideal and passed first time.
some instructers can be a bit dodgy and want to keep taking your money but thats the extreme minority. Try do a single mock test with a different instructor, see what they say