New wiring feed

[TheAngryDog]

I want to create a new switched live into the cabin of the car, so that I can run a second Accessory socket and run some gauges.

I could take these off the existing cigarette socket wiring but I'd rather do it properly / safer. The car is a 2006 Mazda 6. Does anyone have any suggestions on the best way to do this please?

Thanks.