So I just bought a new thermostat for a rad in my house upon trying to fit the new thermostat the connection nut on the actual rad is too large for this new thermostat. The pipe coming up from the floor is 1/2 in but the connection on thr rad is 3/4". Have looked on screw fix sbd they don't seem to do 3/4 thermostat that fit an older rad. Is there a 3/4 to 1/2 union adapter you can buy as I can't find anything??