[russellb]

Hi,

The debug output of serial monitor is human readable, try open it at 19200 baud.

The wi-fi is not showing up on scanning my network.

That is the normal behaviour, the device runs in ST (station) mode not in AP mode.

Do you have any Transmitter unit already sending data?

If you have a multimeter, try measure the output voltage of the 3.3V regulator.

OK works much better at 19200 baud.
I had already checked voltages, and 3.3 v seems OK.
BUT I found when checking the BME280 it was not plugged in.

I2C_scanner found a device at 0x50 so  I set that as display address.

I have put the Wi-Fi credentials in, but it's not showing on my network.

Debug output shows:

Code:

ESP8266 FW Version:
Mode station ERR
Multiple mux ERR
Join AP failure
WiFi connection is OFF

From what I can see "Internet" is enabled.
I presume I'm missing something. 
There is a little blue LED near the Wi-Fi antenna which blinks on booting, and I have noted it flashing occasionally