Moisture meter....

[Ajax123]

I've emailed a couple of meter supply companies to see what they recommend.

I've only come across a few anhydrite screeds over the years, they don't seem to be very popular for some reason.
The 2 I have tiled I used ditra mat as timescales were critical, still work for the people involved with those so would know of any problems.
And 1 I quoted for and supplied a lot of specifications for, I didn't get the job. The customer went with another tiler that said all this prep is unnecessary and no need for the matting. I pleaded with the customer to do his own research and ensure the other tiler did the proper prep, and told him I wasn't bothered about not getting the job.
Don't know how it all turned out, but I definitely know it wasn't dry enough To tile directly onto

Not Popular?? about 25% of the overall UK screed market is anhydrite. Last year something like 2.5 million square meters was laid. Much of this was in single houses so lots and lots will have been tiled. As you say though if the customer has rushed it and the floor has not been prepped then it will fail. You are best off out of that particular scenario. Where in the country are you. Something like 50% of the anhydrite laid last year was in London and the South east..

 

[Alphadock]

I'm south. Just my experience, I've only tiled around 200sq/m of anhydrite over the years, and 10's of thousands sq/m on sand/cement.
I mostly work on refurbs, extensions and one off new builds, not the big developers. So it could be because the builders are stuck in their old ways