Hi Mooshie
Thanks for your reply. No, he doesn't have a dummy and hasn't since about 1 y-o. He used to have terrible dribble rash on his chin but we've conquered that because he's dribbling a bit less i.e. we don't have to change his shirt 3 times a day!
I'm going to research more on the internet and persist in trying to get him to swallow properly. Surely he'll get sick of me nagging him to swallow that he'll start doing it automatically. If not, then we're off to a specialist.