Checked with my friend and it is 120 sq mtr for the Ufh. Apparently it is only the manifold that needs wiring as the new wiring was run in at first fix for the new boiler etc. Once boiler was fitted they were just wiring it from wires already in situ.
Thank you for your reply :) The whole thing is from scratch, it is a brand new system with no previous c/h. The house is vacant. No plastering done. No ceilings in. Boiler on ground floor cylinder immediately above boiler on first floor. Ufh manifold within 4 meters direct sight of boiler...