Couple of quick thoughts. When the BA plane lands, try to get to immigration speedily. On my last trip to Aus, SWMBO decided to go to the loo before immigration. Mistake! All the advantage from exiting quickly from J was lost. Back of the queue! So go to the loo on the plane, not before immigration.
When the BA plane arrived, there were some mobility folk at the gate, but not many. It is a smallish airport, so not many helpers around.