Sorry guys my bad it's all hive!
Underfloor heating controls -
https://www.advancedwater.co.uk/STOMEMO/A660-454-0001/P-2216%20UK%20Hard%20wire%20master%20PPL_IMP_0882D.pdf
Hive receiver - image below.
I have looked at the back of the hive receiver and can see that it needs live, neutral...