Moving from Nest wireless downstairs with upstairs wired thermostat

Our Nest packed it in, so I’m looking to shift to Tado but I’m unsure about what to buy. Our setup is this:

Originally our Grant Multiboiler had two wired (Honeywell) wall thermostats, one upstairs and one downstairs. This was changed to a downstairs wireless Nest with the heat link installed at the boiler. (The downstairs thermostat was rendered inoperable and there are just some capped wires sticking out the wall).

Upstairs there is also an immersion water heater near the wall where the wired thermostat is but I don’t think they’re related as there is also an electric switch to turn the immersion on (half or full) and off.

I think it would be best to go back to two wired thermostats so a Tado would get installed where the old downstairs thermostat was and the Nest heat link removed off the boiler (presumably some wiring would have to be reconnected). Then an extension Tado kit for the upstairs wired thermostat would be installed as well.

This would allow me to independently control the heating in the two zones. Is this possible? Otherwise would I need to take off the Nest heat link and install a wireless Tado downstairs where it was next to the boiler and then have a wired Tado extension upstairs?

Thanks for your help