https://uk.rs-online.com/web/p/specialist-drill-bits/0569792
These. And they self-centre, pretty much, if you're making bigger holes.
I've only ever used the diamond ones on glass tiles - Even with my heavy-handedness, I've not managed to crack ceramic tiles with the triangley bits.
@NotThamesWater started
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https://uk.rs-online.com/web/p/specialist-drill-bits/0569792