I've designed a basic board around the ESP8266 and had three produced by Ragworm in the UK.

The first, I've incorporated into the Sensor Module, which I'm pleased to say is now working fine. Environmental data is being send to my message broker every 15 seconds. I've some concerns about the temperature readings, which may be a little high. I wonder if the airflow in the enclosure isn't quite enough and it's heating up. I can always add some more ventilation, or even bring the sensor out of the enclosure, if necessary.