I do not have the BPP workbook (only the Revision Kit) and so I do not know what is in the essential readings section.
Our free notes and lectures are a complete free course for Paper FM and cover everything needed to be able to pass the exam well. If you are watching the lectures then you do not really need the workbook – it is only the Revision Kit that is essential, however you choose to study.
The only extra reading that is worthwhile is to read the technical articles on the ACCA website (although everything in them is covered in our free lectures anyway).