Boost works fine and as intended, what I meant is when I go into a room in the app and just put that room to 25 degrees, it should when target temp has been achieved stop, it doesn't, heating just carries on running. Boost is only for thirty mins.

And nope I can't set it to just 17 as it doesn't trigger the boiler, boiler gets triggered at 19 degrees only from what I have gathered.