Sorry you've not had any responses about this. Are you sure you've posted in the right place? Here's a link to our subject forum which should help get you more responses if you post there.
Look at the details here: http://www.admissionstestingservice.org/for-test-takers/bmat/ As it takes place in the Autumn there is time to revise for it as well as working on your A levels. If you want to take it this year you have missed the main entry deadline but could still enter.