@RandomGrinch hasn’t been on for ages (I hope he’s ok). You’d probably be as well ripping that shoite Esi wiring center out. Unless of course the Tado can provide the 5v?
Hard to follow, but I think it looks correct. In your 1st diagram, there’s is no 2nd wire in WC1/Zone 1 terminal 3, whereas there isn’t now, so should be ok.
Can you grip the nut underneath and turn the tap at the same time? Or twist the tap from above until it hits the tiles/wood or mallet and then keep turning from above?
Finally, a bit of sense. As I said, you have no neutral and a CH off. Inform the builder he has done it wrong. If it was swapped on the backplate, the replacement would work unless faulty.