That isn't surprising around here, I'm afraid. There are a number of "experts" who like to find ways criticise everything they see on here. I'm not entirely sure why they visit so frequently if only to be unhelpfully negative at every turn. I suppose there's always a risk that someone might be...
Our cyclinder stat has a permanent live. It automatically heats the water up to 60°c once a week regardless of any input from my nest. Also, our frost stat is connected to our HW so when it drops below 10°c in the garage (where the boiler is), the HW will be heated.
Last week ours was coming on...
John - don't stoop to their levels and entertain their needless questioning of your ability. It's a shame but many of the experienced plumbers on here are bitter and twisted about one thing or another. Not to mention being against anyone who might be able to do the same job as them.
Congrats on...
Is there any harm in him asking here? There's nothing wrong with asking questions about these things and people should be encouraged to research things and ask questions outside of the classroom as well as inside it.
The C&G textbooks are pretty good but includes a lot more information than just wiring regs but do cover everything you've asked about those tests.
https://www.amazon.co.uk/City-Guilds-Textbook-Electrical-Installations/dp/0851932835/
I speak from a purely cosmetic stand point. Compared with every alternative Nest, Tado, Evohome and even normal room stats, it looks like it was cobbled together by a blind elephant with a heavy cold.
Just because he was a part P qualified electrician, it doesn't mean he knows anything about wiring up heating systems. Sounds likely he didn't!
Glad it's all fixed :)