Where to start!   NEVER done wall tiling in my life so here goes.    Setting a datum:   I've taken the datum to be the centre of the big pocket alongside the bath as this will be the focal point:     I've set the laser up on a clamped piece of wood. Tbh a pita to keep doing it. Should I set up some sort of permanent platform?     The width of the laser line is nom 1.5mm. Is that "good enough"?