No power to stereo

[CMB]

All the parts came today to fit my old single DIN stereo into my MK5 GTI, this is the wiring harness i bought;
http://www.caraudiodirect.co.uk/con-ct20vw01-ct20vw01-harness-adapter-vw-passatgolftouaregtouran.html

It all seems to fit but I'm not getting any power to the stereo at all, there is a 12V switched wire thats just hanging around but surely that doesn't HAVE to be plugged into something (fusebox etc.) thats just so it switched off with the ignition isn't it, without that wired in i should still be getting power through the constant 12V shouldn't i?

Cars in bits and I'm going back to uni today so its a long drive, going to be made even longer if i don't have music :(

[robump]

Don't quote me on this as I am by no means an expert but I've been reading up on this to change my rcd300 to a single din and I think they recommend the ctvw002 in this threadhttp://www.golfmkv.com/forums/showthread.php?t=170712

As I said I'm by no means an expert but that thread was very helpful.