One other thing that might be of importance is there was an aftermarket radio in the car which I removed, when I put my one in it had no power going to it, so I tried the old one which still didn't work. I took it to a car audio place who said something about a switch on the ignition? And that instead of replacing it it was easier and cheaper etc to just wire the radio to the ignition. Something along them lines.
Not sure if that's relevant, thought it might be as it wasn't getting any power. But it works fine now even with the fuse blown. Also does anyone know what size fuse is supposed to be in the slot? Cheers