Aside form the fact that you would have to buy a second hand set of ATPL manuals (which could be out of date) and then another set when you enrol on an ATPL course, I think it would be too much.
It will be harder for you to pick out the aspects of the PPL syllabus which are relevant to the PPL exams plus, for example, Air Law at PPL level is UK based whereas at ATPL level it is ICAO based so there are some differences.
Cheers
Whirls