1) The dummy may work, you might be surprised.
2) When pups are taken from their mother, they miss the heartbeat, so ticking clock in puppy cages is often used to wean them away from their mother. The dog sounds a little old for this, but you might try it.
3) Give him something to do when they go out. Chewtoy, snack, pick something, it may be barking because its bored, if this is true it may work.
4) See if you can borrow a bark supression collar from someone. They electroshock the dogs throat if it barks, I'd send you mine, but its a long way to Scotland, and you'd need a transformer to step it down, etc. I'd tell you to buy one, but in actuality you probably wont need it but for a few days, unless the dog is a cronic barker, he is going to learn in a few days to not bark and you'll be set.
-Tig
