It's rocket science to me, but I take your point - I'll see if I can find
someone local to do it, thanks.

IIRC Ikea do an upstand to match their beech worktops. Ugly looking
thing of the same thickness as the top. Why not just tile down to the
worktop?

Any situation where two surfaces meet and water is involved seems to
result in the joint discolouring and perishing. I'd rather pay more for
something seamless. Same with the sinks - undermount only in that case.