14 hours ago, Oz07 said:

crack just anywhere

That can be controlled by putting in crackbinducers, esp at doorways.

Our own floor over screed is 12mm thick tongue and groove, including mm oak veneer. Glued down onto screed that has had 8 weeks to stabilise.

1 hour ago, Oz07 said:

I thought you had to have floating on top of ufh? I like the look of parquet flooring in the smaller traditional size but all the modern floating stuff seems to be massive planks

Mine said clearly to glue down. Floating you have lots of air gaps and they hinder heat transfer. 5 years of heating and cooling, look as good as when installed