In reply to henwardian:
Ikea is a very expensive way of going about this. If you can use a soldering iron I would go for a combination of simple 12v downlights from screwfix but replace the halogen bulb with an LED one off ebay.
Then for mood and ambient lighting go for LED strips which are low power and easy to install and look good. Lot's of colours available and you can put them anywhere. You can even get flashing ones operated from a remote control.
See here:
Check out ebay as this site doesn't let you post links to it.
My set up uses about 12-14W on ambient and about 20W with other stuff switched on. I also have other lights and total installed power is about 60W but most of that is for fun.
I have installed a voltmeter and ammeter and done all the wiring myself. Zig units and so on are a total rip off and you can build your own system and make it better for a lower price.
Here is my van.