Fitting a head unit in a mk2 golf, i'm confused!

[gc350]

The original stereo was not working so i decided to fit a head unit that i already had.

I'm a bit confused now.

In the car there are three wires
Blue/white
Red
Brown

On my head unit i have four wires
Blue
Yellow
Black
Red

Any ideas which ones connect to which, i dont have a manual for the car, and i can't find the headunit one.
(oh yeah, theres the speaker ones too, but i can figure that one out.)

[Dizzie]

on your headunit:

yellow - permanant live
black - earth
red - switched live (ignition, +15 wire, 2 black ones coming off the barrel)
Blue - Electric aerial or more commonly the Amp remote wire

In your car:
Brown - earth
Red - permanant live
blue/white - switched live (ignition)

not 100% sure on the blue/white as the haynes isn't helping. connect a bulb to it and earth the other side. then turn the ignition on.

A better way is to fit a ISO connector straight to the fusebox, earth and ignition barrel properly soldered. you can fit any radio easily then.