It is a standard Philips stereo/CD changer in a 97 cloverleaf. The front driver's side and the rear passenger side speakers are the only ones that work. No obvious loose connections and sticking a multimeter on the back of the stereo the positive and earth tabs for the speakers don't seem to match with where they should be according to the sticker. As you can tell from the post I'm no sparkie so what should I be looking for? Cheers,
Given that the rear speakers are usually the wrong way round in most 145s, check that the balance on the radio is in the center. I know this sounds too simple but it would explain why the speakers at opposite corners are working and the others aren't.