I fitted one of these.
https://www.plumbnation.co.uk/site/honeywell-cm927-wireless-7-day-programmable-room-thermostat/?gclid=CMi1743cucQCFXQatAodJ0MAcQ
Wireless to the boiler, 7 day 6 program timer, party function, holiday function.
It's not controllable from a phone but we don't need...