Does anyone have any tips for teaching my puppy 'down'? I have tried lowering a treat from his nose to his front paws in a sit position but he just gets up and backs up. Any suggestions?

It's worth waiting with the treat on the floor - sometimes they lie down to try to open your hand for the treat. Otherwise you can sit on the floor at right-angles to him, with your knees up like a bridge (if you see what I mean), have him sit then hold the treat on the floor just the other side of your knees so that he has to lie down to crawl under your knees to get to it ... clear as mud probably!

I always put my hand on their lower back while they are sitting and then with the other hand do the treat from nose to ground trick then drag the treat very slowly along the ground away from them. I do not push down on the back at all, but it just encourages the puppy's back not to push up or back up (don't know if that makes sense). Then when the puppy is down I stroke the back saying the command 'down' while the puppy is chewing on the treat.