The message
from guv contains these words:

One reason I think they may not be porcelain, is the fact there is a
definate side they need to be laid. ie they have ridges like you would
find on ceramics to help adhesive adhere to them. Is that normal?

The Italian porcelain tiles I laid in the conservatory are one-sided.
They're pressed from powder and then fired. Incredibly tough [1] and the
colour goes right through, even on speckledy tones, so chips and wear
won't matter.

[1] Though I planned to use the diamond tile saw all along, I thought
I'd try to score and snap one. Even my rather too massive frame couldn't
bust one. I guess because they're homogenous there's less reliance on a
surface skin to maintain the strength. They're cerainly tough.

--
Skipweasel
Pay no attention to that man behind the curtain.