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Just use a thicker layer of self-levelling cementitious screed.
The more different materials you use the greater the chance of subsequent adhesive failure.
The joint over the change in substrate needs to be filled with something better than 'silicone' sealant, which has poor long term, un-primed, adhesion.
The more expensive, (but vanishingly cheap in comparison to the £1k of tiles),
MS sealants are more liekly to give good longterm unprimed adhesion.Bear in mind any quoted MAF, (movement accomodation factor), is the total movement across the joint, so 25% MAF for a 5mm wide bead of sealant gives just over 1mm, (1,25mm), of total movement, (expansion and compression).
mespilus
One of the reasons for the ply is that with adhesive the tiles are 12mm thick or so, and the adjacent wooden floors are 25mm. So I need to add something like 12mm to make the floors all roughly the same height.