OK, I think this is good news.
The new module doesn't have DE / RE pins, rather it relies on the TX to tell it when to switch to send / receive mode.
It does seem to properly switch back to idle though. 
ALSO...
After some head bashing / panicking it would appear that actually the controller is working at 9600 baud with an ODD parity bit and I'm now able to immediately add a UART decoder with no frame errors!!!
It does mean that I now need to go back and re-analyse the mixer / controller traffic but that should be fairly easy.
Watch this space...