I studied for the E3 exam using BPP 2010 syllabus book but had to supplement the knowledge from the Internet as there were some gaps between the textbook and the Acorn revision kit I bought (written for the 2015 syllabus).
For the F3 and P3 exams I used Kaplan’s new study materials plus Kaplan and Acorn revision kits.
I am glad I did invest in new study materials because I managed to pass all three OT’s first time.