What is all lombard street to a china orange ?
Lombard Street is in the business area of London, and the Bank of England is there, so if you bet all of that (a huge amount of money) against a China orange (something of little value), you must be pretty sure you're going to win.
Australian slang dictionary
I haven't heard the Lombard St. one.
Oh, and here:
"The Sydney race caller Ken Howard is credited with the phrase London to a brick. Brick was Australian slang for a £10 note (from its reddish colour), and so if, towards the end of a race, Howard claimed that the odds of a particular horse winning were London to a brick, he was saying that the horse was at extreme odds-on, with an indisputable chance."