Hi Jez, waht you need to do is place your tile on the cutter as if you were going to cut it. FIrst unscrew the breaking adjustermost of the way out, move the incising arm all the way to the braking position and rest the breaker on the tile. Then applying LIGHT pressure to the handle with your thumb andhave your index fingure underneath the main bar, screw the adjuster in until you can JUST feel the handle start to lift. When you get to that point, ease back the screw until the breaker is JUST touching the tile; back off the screw a fraction more - no more than 1/8th of a turn - and lock the adjuster into place.
This should give you the correct position to break by pushing down on the handle. Try it out on a spare tile to make sure it breaks cleanly, adjust as required. You will probably find that Montolit say nothing about the extra 1/8th turn as they say you should "shock" the tile by banging the handle to break. This is fine but it tends to hurt you hand after a while.
Grumpy