Maybe he needs a little incentive... Put him to a little challange... Give him a bunch of cheap generic tiles, and tell him that if he can break away 3cm wide pieces undamaged (score first, then nips) from five tiles in a row, he'll get... 10 quid...
If he can make a relatively clean, round hole, with parrot nips in... Three tiles... Which follows the markings you've made (initial hole with a grinder?), he'll get 20 more...
If he can shape a tile into a clean, well formed "C", with only his nips, he'll get 30 more...
50 quids should be a rather good incentive imo, and you'll have increased his competence, understanding of tiles, and the value of him as a worker
