From the description it would seem obvious to redraw (that part of) the (underlying locked) image with the Pen Tool, just clicking each relevant position; presuming horizontal and vertical lines, Smart Guides are your friends, clearly showing the directions.
Thank you for your response Jacob.
It is very apparant that I am clearly out of my depth with Illustrator as I understand what you are saying but lack the skill to implement. I have therefore posted a job to a professional to help me achieve the results I need.
You are welcome, p.