Anyway, I was more interested in the aspect of priming (or not) the ply before the tling. If there are better addy's available I'm at the stage where I can swap what I use.
Hi Simon
I was always under the impression that the back and sides of ply should be primed, rightly or wrongly, I sure someone will be able to confirm this, when layer ready to take tiles ! And that is one of the main reasons , amongst many, why i will not tile onto it because it is never done by the chippy when fixed.