Apart from the primary need of rewiring and all new plumbing and heating, my main focus has been to insulate everything. Then insulate it again
We gutted the house of all wiring, plumbing, plaster etc.
Then started with the hydronic under floor heating.
Ground floor construction from the bottom up is concrete, damp proof membrane, 125mm(5") foil faced PIR with all joints taped, PEX heating pipe at 100mm(4") spacing and 100mm(4") screed (sand and cement with fibres to hold it together when heated).