I would suggest you find a thermostat that does not need a neutral, there are loads of battery powered hard wired units, for wireless unit look at Nest e. May seem odd, but often the old thermostat works better than the new types, as all one often wants is some thing to turn off the boiler when weather improves, the thermostatic radiator valve (TRV) controls room temperature.
The radiators causes thermals so next to radiator it is reasonable indication of room temperature, but the thermostat on the wall measures a mixture of wall temperature, and air temperature and is often no in the best place for thermals to ensure a good representation of true room temperature.
At the moment in my hall the TRV head is reporting 18°C current and 20°C target but the Nest wall thermostat says 19°C, today reasonable close, it depends if doors left open or closed, but have seen as much as 4°C difference as it takes time for the air to circulate. My living room gets the Sun, so today 2°C difference between the two radiators as the sun has heated one half of the room.
Dinning room cold at moment 17°C where target is 21°C as only went from 18°C target to 21°C target at 4 pm and not enough time to alter the room temperature. Even with programmable TRV heads it takes time to alter a rooms temperature and it can only do it if the boiler is running, so likely to get the dinning room warmer, I need to reduce the target temperature in the hall where the wall thermostat is.
Why don't I use a cheap thermostat? Well I use Nest because I only need two wires to connect the Nest thermostat to the heat link to control both central heating and domestic hot water and I only have two wires, it was not fitted because I want to use phone to adjust it, it was simply because I only have two wires.
In the same way if you don't have a neutral, then easy way is use a thermostat that does not need one.