BPP exam kit edition

Sept 2020 to June 2021.

Is there much of a difference between both Actually I was thinking I should leave some margin just in case I fail in June, I can use it again..

There won't be a huge difference as the syllabuses haven't changed very much. Provided you look at the 3nd of the Sept 2021 to June 2022 syllabus and note the changes, you would be able to use the later book ok.