A typical situation at the moment is setpoint at 20.0 deg, temp shown is 19.3 deg and there is no call for heat. This is because it thinks that the actual temp will keep rising following earlier call. So you end up putting the temp up to 20.5 deg to get it going.
I think it is fairly well documented that the Digistat+3 uses logic to estimate overshoot. So, for example, if you have the temp set to 20 deg, it will turn the heating off at 19.3 deg because it expects the temp to continue to rise. The problem is that it's logic doesn't work in the real world...
Having had two of the 'original' Drayton Digistats which worked very well, I've now had it with the latest model that tries to guess whether the heat should be on or not and gets it wrong most of the time.
What's a recommended digital thermostat, 7 day programmable, that doesn't have built in...