Interesting. Maybe a cm927 would be better as the temp drops slower in my lounge than the hall where the present stat is, so it would come on less often.
I do think you are turning a molehill into a mountain.
The difference in the amount of gas burnt will be negligible, so it will take many years to recover the cost of purchasing and installing a different thermostat.
Just forget about the boiler going on and off and let the thermostat get on with doing what it's supposed to do.