This is a long shot. We have just been informed that Gulf Air have changed their flights and we arrive in Bahrain 10 hours after our flight leaves from there to frankfurt. So. We are now booked to fly from Sydney the day before (Saturday) and arrive in Bahrain at 8.00 am. We then have from then to midnight to kill in Bahrain. Any advise on what to do in 12 hours?

Sorry not much to do there on short string. The only place to fill the bill might be the souk (marketplace) includes a gold souk and cloth souk.
I also do not know any immigration restrictions for air traveler stop overs and for what sounds like a quick in and out!