The BMAT has provided all the past papers on their website:-https://www.admissionstesting.org/for-test-takers/bmat/preparing-for-bmat/practice-papers/
You can download all the past papers and print them out to do them.
NOTE: I do not own those past papers. They have been provided for free on the official BMAT website.
SECTION 2 ASSUMED GUIDE
They have also provided an assumed guide for the BMAT. This contains ALL of the content that COULD be asked in the exam. This guide is only for Section 2 (Scientific Knowledge and Applications).
The link for the assumed guide:-
The BMAT official website also contains some extra information on the specification and the content that could be asked in the exam. These are ‘Further Resources’:-
There are also some video resources:-https://www.admissionstesting.org/for-test-takers/bmat/preparing-for-bmat/videos/