You can do the rest of the "old" in one or two days! My advise is to buy PPL Questions and Answers by Pooleys and do read each question and explanation properly. After this just do all the test in that section again without looking at answers. Do the mock exam with your flight school and you should be ready!
You have completed the hard ones (Air Law, Navigation, Met) already, the rest are easy
You can make it by 1st Sept!