Hi Mark,
I'm just wondering whether your boy's litter tray isn't big enough... Pearl likes a nice big, high-sided tray with lots of litter to scrap about in. What about a covered tray perhaps, or some experimentation with the depth of the litter in the tray?
Another possibility is that your little rascal doesn't like using a tray that's already been piddled or pooped in, so it might be worth providing him with a second tray and scooping as he goes.
Lastly, he might not think too highly of the litter that you are providing for him. Are you using the same litter as the breeder, or have you switched brands entirely?
Hope this gives you a few ideas to go on.
Witty.