Australia to win the test is available at 3.8 on Betfair, which is too big for me.
England have done very well to get to lunch without losing a wicket, and both batsmen are going along nicely. However, there's still five sessions of the test left, and it's certainly not inconceivable that England will be bowled out before lunch tomorrow. With another 86 runs still to go before making the Aussies bat again, the hosts will still be confident that they'll have enough time to knock off any total that England might set them. England might bat out the rest of the match, but that would be no mean feat, and with the pitch deteriorating it won't get any easier. I'd have an Australian win at nearer 2/1.