Tiling onto uneven? wooden floor

[fluffys]

I have a floating T&G chipboard floor which was lined with quarter inch ply and had old ceramic tiles laid on. We have taken the tiles and old board up but the ply was screwed and well glued to the chipboard and there are areas that will just not budge, leaving bits of glue and residue of plywood in some areas. - is it ok to go over the top of these with new quarter inch ply.

My tiles will be pretty large polished ceramic so not cheap! and I dont want to risk breaking them.

Whats the best way to get my floor nice and flat ready for tiling.

 

[Tom.]

I'd pull the lot up, chipboard isn't expensive.