I bought a Moes thermostat and managed to pair it with Home Assistant, see Pairing Moes ZHT-006-GB Zigbee Thermostat with Home Assistant Yellow
The Moes thermostat controls the underfloor heating only, so it’s not a perfect replacement for the dual control thermostat. However, I found I rarely used the heated towel rail so I don’t mind not being able to control it anymore.