Nice 
How do you solder those little surface mount components?
Thanks. It’s really not easy at all but this was done with a cheap £10 ebay 40w soldering iron. I’ve got a soldering station which has a magnifying glass and crocodile clips and that helps a lot. Other tips are keep all copper spotlessly clean, use flux and good quality leaded solder
These are 0508 footprint 10k resistors, 5 of which are soldered on the underside of the board. I’m not proud of how messy these turned out but they were the most difficult part of assembly…and it still works so at least I didn’t fry it into a completely useless heap 
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@Joe_Lippa OMG - they are tiny!!! Thanks for the replies - very helpful.
Is there a reason, other than size of the board, you didn’t design the layout using normal sized, discrete components?
No probs, for this board size matters. A smaller board costs less to get printed so I spent a while choosing small smd components and arranging them in the best way to reduce the board size. If you didn’t want / need a small pcb then a veroboard / stripboard version would be good enough, which is what I started out with as a prototype: https://jjssoftware.github.io/esp8266-configurable-power-management/
Thanks for the link - I’ve added that to my esp list of interesting links 
I have built a temp/humidity monitor for my polytunnel on vero board, but I fancy the idea of making a PCB and adding a barometer and light meter as well. Then I want to build several copies of a different kind of board, still using ESPs, to attach to capacitive soil moisture probes so PCBs would be almost mandatory. But size isn’t a massive issue so I might just bite the bullet and pay a bit more for a bigger board and less eye-strain 