Unfortunately this all happened during the shops shutdown and my choices were severely limited. The store was doing deliveries only, but with a minimum order value way above what I needed. They told me they had the blue spiral drills only.
To "expedite" the delivery process and get around the delivery charge I had to drive to the store, park in the car park across the road and call them. They sent a small van across the road and "delivered" to me, taking cash on delivery. =D> =D>
I have many of the matt alloy masonry drills, none of them would penetrate these tiles. After literally throwing away a half dozen or so I found an older, obviously steel bit. That drilled a half dozen holes before it too just wore out. In all my life I have never worn out a masonry bit before.
These tiles when finally cut produced a very fine white powder that made me think a lot more of resin rather than clay. The makita disc cutter made hard work on them with a diamond coated disc.
I had to drill two 40 mm holes for radiator fittings, and used the carbide kit from my builder friend. They went through with very little effort. Unfortunately that kit didnt go below 25mm, no good for mounting toilet roll holder screws. :roll: