Stef, if I use the Anhylevel to bring the floor height up, do I still need to use the Ditra matting as well, or can I use just a Anhydrite adhesive straight on top of the Anhylevel?
It's always reccomended to uncoupled a screed with ufh so I personally would fix ditra with anhyfix then use a suitable cement based adhesive to fix tiles to ditra.
Stef, if I use the Anhylevel to bring the floor height up, do I still need to use the Ditra matting as well, or can I use just a Anhydrite adhesive straight on top of the Anhylevel?
It depends on what tile you are using, looking back you say porcelain tiles so I wouldn't use Ditra.
What I would do though is get a pro in as you have already spent a considerable amount of money & you don't want to do it again.