Still no luck with the potty although Zachary seems happier to sit on it - at times. I've been getting Leo to sit on it as well when they're getting dressed, and did again at bathtime tonight to try and encourage Zachary. He seems to respond to "look, Leo's doing it too," more than "you're doing it on your own because you're the big boy" type stuff. Leo thinks sitting on the potty is hilarious and at bathtime I almost thought he was going to do a wee! Would be one up on Zachary..
Also bought a book today - Pirate Pete's Potty to read with him. But I'm getting more convinced that while the pull-ups are catching everything, he's got no motivation to use the potty or toilet. I suspect that I'm going to need to move on to proper pants soon and see how that goes when he starts getting wet. An afternoon in our kitchen with the tiled floor I think, although it won't be for a few days. Will stick with the pull-ups in the meantime - I don't want to go backwards just yet.