Didn't get round to another session yesterday, but did one this morning, and boy, did he remember what he had to do?!!!
So, I think we can safely move on to the next stage, which is getting him to actually pick up the dummy. Watch this space....
BTW I'm hoping that if we can get him to bring the dummy to us and give it up, it may help with his guarding issues - well, I can dream, can't I?