Transformerless power supply

[Parmin]

There are some small transformer based psu inside some LED lamps taht can be salvaged for this purpose.
Or you can buy them cheap on Ebay, since you are going to go with transformerless anyway, this might solve your problem albeit not being as dangerproof as a well designed transformer psu.

[Wizpic]

After looking into this more, I think I've decided and found the way I think is the best and safe method is a Vigortronix VTX-214-001-105 1W AC-DC Power Supply Single Output 5V transformer from here

https://www.rapidonline.com/vigortronix-vtx-214-001-105-1w-ac-dc-power-supply-single-output-5v-84-2686
a bit bigger than I'd like but the safeest method.
Also instead of using and Arduino and NRF24L01 I will now be using the wemos D1 mini to control single lights and sockets on downstairs and using the other method for the upstairs where I can use one Arduino and NRF24L01 to control 5 lights