Hi guys
Thanks for your respective contributions.
Just to add to the mystery - I've located a copy of the original hard-back version of 'You'll Die in Singapore' -
Page 204:
Two bright, staring eyes approached rapidly, then flicked off as the dark bulk of the SUNDERLAND drew near us, the white curl of sea writhing away from its hull ... There was a chink of metal from the side of the aircraft, a door opened and a man in khaki shorts leaned out. An Australian voice cut across the velvety waters ... Are you the two fellows we're taking back? He asked.
So, it wasn't a Catalina after all (McCormac would have obviously known the type) and unlikely to have been a Do24.
Over to the experts, once again.
Cheers
Brian