Bathroom Floor preparation of sub floor ready for tiling

[Spinny]

Bathroom floor. I would be grateful for advice on how to prepare my bathroom sub floor ready for tiling.I have removed the floor boards and plan to lay 18mm WBP plywood.The question is, what should I lay on top ( if anything) before I lay 6mm tiles. I want to avoid having too much of a step up into the bathroom, that's one of the reasons I decided to take up the floor boards.
A picture is attached showing the floor boards removed. I will be adding noggins before laying plywood sheeting
thanks

 

[Tile Marble Granite]

Install anti crack membrane Ditra matting, any brand would do.

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