Looking at this again it seems the thread is not blocking. I logged my asynctask in the main thread as it ran and I can see it’s polling alternately with my connectedthread. Though the behaviour is unexpected - I’d expect the main thread to catch the CONNECT event but it only does this for the first connection, then the connectedthread catches everything which is odd.
Sleeping at the correct moment seemed to fix it, but it seems very fragile (and the sleep is too long), so back to the drawing board.