Ok, so this is an age-old-topic for discussion, and I've read through
most of the old posts on this forum, but I'm still interested in
people's experience.

My plan is this. I have a large chipboard kitchen floor. The floor has
three particular faults - firstly: where two large pieces of flooring
join in the center there is a slight ridge (very very slight, I mean
about 1.5mm ridge). This spans the length of the room. Secondly: under
the fridge-freezer there is another ridge where the floor declines
slightly for some reason... and thirdly: when I walk across the room
(on the bare floor) there is movement in the floor.

Anyway, I know tiling on less-than-perfect wood floors is a recipe for
disappointment, but I'm going to do it anyway. My plan: 12mm exterior
grade ply screwed at 200mm centers max in large (2.4m) sheets to
minimise joints. Then a PVA seal applied to the ply, followed by 330mm
square ceramic floor tiles with a flexible adhesive and grout. I may
position the tiles so that they meet over the very slight ridge
(instead of having tiles span the ridge) so that any cracking is
centered on the flexible grout (or should I do it the otherway around
since tiles themselves are less likely to crack... aren't they?).

Any experience of advice appreciated.