Market subscriptions - are always in underlying exchange currency - GBP. The default roll-up for GBP is £2 for batb / batl and bdatb / bdatl, This means that stakes of less than £2 (or currency equivalent) are rolled up to the next available price on the odds ladder. For atb / atl there is no roll-up. Available volume is displayed at all prices including those with less than £2 available.
Orders subscriptions - are provided in the currency of the account that the orders are placed in.
Support for Australian Exchange markets isnt provided via the Exchange Stream API.
Runner Removals on the Order Stream