I have a nest thermostat too and I love it. We’ve saved so much with its eco mode 
Our heat link stopped working the other week and I dreaded the cost of getting a replacement and having it reinstalled. I thought I’d try my luck with Google support and the level of service I received was first class.
Not only do you yet a personal advisor assigned to you but they do video calls with you to help diagnose the issue. They actually chase you for bits and pieces instead of the reverse too.
In the end they paid for everything. Replacement part and the cost of the plumber who originally diagnosed the issue and again when they returned to install the replacement heat link.
In addition to this they gave me a free stand too that are around £40 as we had a cheap Chinese knockoff one.
So even if things do go wrong, you’ll be well looked after.