Re: Allow me to point out something...
I live in a 3 bed semi with new windows, full 12" loft insulation, 100mm external insulated walls.
Your house doesn't get much more insulated than ours. I have done my calculations on real figures and the Nest paid for itself in a year.
I didn't buy it for cost savings, I just thought it looked pretty and I liked being able to control it with my phone. I very rarely use it via my phone as my house is well insulated and stays a consistent temperature. The dial only gets touched when one of us is ill and feeling the cold. But the auto-away feature is what saves the money.
You may hate Nest, but the fact is that smart thermostats work. The ability for it to automatically turn off the heating when you are not in the house and you forget to turn it off before you leave will save energy and money for nearly every household.
In general I'm pretty lazy when it comes to saving energy, but if it is more efficient and pays for itself, then it's a no brainer.
The only argument I have against them is the theoretical spying capabilities it adds to your house. But then with the amount of other internet connected devices I have at home with microphones and cameras, it is just one more addition to worry about.