If you use a control unit (like PMS3) then the internal wiring is fairly straightforward - everything wires in and out of the PMS3.  I had a Split Charge Relay fitted so the Leisure battery can be charged from the alternator. 

Fusebox

Use Grommets to protect wires

Intercom which can be switch to play internally or externally

Light monitor panel - works!

Put the red light onto a separate switch for nightime use

Speakers

To get wires through roof run a garden hose first and grease 12v wires before threading them through

Get wiring in early

Route the wiring

12v LEDs

Replace bulbs with LEDs

New sidelights

12v for light fitting

Light fitting - each can be separately switched

Put in 12v USB sockets

It has Cruise Control. The yellow thing is the handbrake

Driver control panel

Electrical cabinet. Easy to take 12v feeds from the middle bars

Fan not working - need new motor...

Label wires - makes it easier to figure out where you cocked up

This foglight switch was too sharp