The OATS notes are very good, but before buying anything it is important to be sure that the product will enable you do whatever it is that you are planning to do with it.
Unless you satisfy some rather demanding criteria (essentially already an ATPL holder with a great many hours in multi-crew aircraft) you will not be permitted to simply study alone then take the JAR exams. The vast majority of students are required to undertake formal training before taking the exams. Exam application forms from such students will not be accepted by the CAA unless they have been signed by the CGI of an approved school. The training may be full time or distance learning.
If you are unsure what training you are required to do, you should visit the CAA website before buying anything.