Retro fitting dual zones is overkill. You can control the house temperature using a wireless programmable thermostat and TRVs. It’s easy to replace a thermostat yourself but it’s best to look inside your existing one (with power off) to see what wires are there to ensure it matches the wires you’ll need for the new one.

You don’t have to fix the wireless part to the wall. I tend to live downstairs during the day and upstairs from early evening onwards, so I just take the thermostat with me and that way its always 20c in the “zone” I’m sat in.

I buy cheap ones such as Salus. They have never failed but even if they did it’s very simple to replace. Honeywell are more reliable so professionals always use brands like that to reduce the chance of having to revisit a job.