In message , at 08:58:59 on Fri, 9 Oct 2020,
Jeff Layman remarked:
I'd use a programmable thermostat in the living room then either
remove the existing timer, or set it "on" 24x7.

Sounds a bit complicated.
If you don't want the wifi integration fair enough, the models
without
that are certainly not complicated, e.g.

https://www.thefloorheatingwarehouse.co.uk/acatalog/info-Slimline.html

You forgot to add the link to the receiver required to work with that
Heatmiser transmitter; both would total around £70.

Wouldn't it be possible to wire it to the boiler, so no
transmitter/receivers required?

I already have a wire [2-core only] from where the timer (or
timer/thermostat combo) is going to be installed, to the boiler.
--
Roland Perry