@willbishNo it is due for delivery in the next few days..... was just reading through @PeterW recomendation https://www.wundatrade.co.uk/shop/home/20mm-eps-400-overfloor-board/
and just trying to work out the best possible outcome with a MAX floor build up of 130mm
so far i had
Insulation 90mm (probably two layers with cross battens) attached to floor
Some sort of sub bace wood under floor 18mm attached to battens
Wunda underfloor heating board 20mm glued to sub. Flo