Yep that's what I'll probably go for, and use the Vitrex levelling system which is 1.5mm by itself. Seems to have good reviews on screwfix. 3mm is too big for such nice tiles imo.
Before you start........measure some tiles. You might find that they are not all 600mm. Some tiles that size can be 599 and 601. That's a 2mm difference. So be careful. Good luck.