Dave, you posted the link to TCNA. Here is the link for their affiliated school, the Ceramic Tile Education Foundation.
Ceramic Tile Education Foundation Home
I have been there for numerous classes over the past 10 years, including a private training session sponsored by Schluter Systems.
What are the training opportunities available in the UK? The other major players here are either going through a union or the CTIOA
Ceramic Tile Institute of America CTIOA - ONLINE .
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BTW, what restrictions or requirements are there for tile setters in the UK? For the most part, here in the US you can call yourself a tile setter without having to prove or demonstrate any competence to anyone first.