with my faq, step 1 identify which fusebox it is. skip to page 2 and compare what you have to the pictures. once identified, you then know which section of the faq you need to check to find the fusebox rear pins. for a picture of the back skip to page 4. (reason its on page 4 is originally there was a link to a page from then bentley website for each section, but they took it down. so i had to put it on page 4 myself)
what you are going to have to do is trace all these wires yourself, and figure out where they go. we cant help you unpick the previous owners bodges im afraid
once you have stripped out all the crap, use my faq to identify where the stereo wires come from and locate these, then wire them into your stereo. what i would do in your shoes is chop out an ISO plug from the scrappy and solder this onto whats left of your loom, then you wont need to faff ever again. the next owner will thank you for it also
