Hi Allan
Yes you can get free visa on arrival with your british passport.I am an Indian guy living in dubai past few years and got recently 190 visa and heading perth in coming months.If you are interested and dont have any arrangements i can take you around the city and drop you back in the airport. I Dont know anyone in perth so trying to make as many friends as possible.If you have your arrangements i can atleast guide you which places you can visit in this 12 hours.