Thank you.
It's a little difficult to see, but I wondered if you could confirm that there were three brown wires in terminal 1 of the wiring centre?
You could, but it would only control the upstairs zone and you would still need to move a grey wire in the wiring centre.
It would probably involve more work and disruption, than connecting the Wiser directly!
For the minimum possible damage, you can leave all the existing wiring in place and simply remove the batteries from the T3's; the Wiser would then completely control both zones...
View attachment 372304
With a short length of 4 core and earth flex, you would...
Using the brown wire, connect terminal 1 of the wiring centre, to L on the Wiser Kit 3 backplate.
Using the blue wire, connect terminal 3 of the W/C, to N on the Wiser.
Using the green/yellow wire, connect terminal 5 of the W/C, to the earth terminal on the Wiser.
Using the black wire, connect terminal 8 of the W/C, to terminal 1 of the Wiser.
Using the grey wire, connect terminal 9 of the W/C, to terminal 3 of the Wiser.
It doesn't matter initially which wiser zone controls the upstairs or downstairs - this can always be changed within the app.
If you did eventually wish to decommission the wiring to the existing stats, you would disconnect two of the brown wires from terminal 1, and the black wires from terminals 8 and 9 - parking them all safely with the grey wires in the spare terminals at the other end of the wiring centre.
Check that all these wires come from the same two cables - a separate brown wire in terminal 1 will be a live in - you still need that one.
I hope that makes sense.