I just opened up a file that I haven't touched all year and noticed that some of the textures were missing but some were still present.
All the textures in this scene are stored in the same file :
F:\COLOURBLIND\MAIN\NEW_SCENES\01_INTRO_ANIMATION\Tex
However, when the file was originally created last year , it was in a different SSD (Which was replaced due to it's small size) and the folder "new_scenes" has since been renamed to "final_Scenes" , so the current path for all the textures in this scene is :
E:\COLOURBLIND\MAIN\FINAL_SCENES\01_INTRO_ANIMATION\Tex
This appears to have confused Blender somewhat , but I found it strange that some of the textures were missing whilst others were not , so I did some investigating.
If I select an object with a MISSING texture then the path for one of its image textures is indeed the old path and Blender tells me it cant load the image : 
BUT , If I select an object WITH textures , the path is completely different and only contains the path from tex onwards :
Now I remember it being something to do with the double \\ being "relative" or something but I don't really understand it.
The issue I have is that this scene has a lot of objects that require re-linking of textures , and there are several other models in this project that will have done the same so I will have to re-link hundreds of textures .
So I have the following questions :
1. Is there a way to fix this issue and re-link the textures quickly? (I have Remington Graphics "Nuke" addon which is designed to help with these issues but the search for textures function is under development and wont work)
2. How has this actually happened in such a way that some of the textures are fine whilst others are missing, - especially considering that this scene was all created at the same time , in exactly the same way and all the textures are in the same folder.
3. Is there a way I can avoid this happening in the future as it seems that changing a folders name can really mess things up on a huge scale....
Thanks in advance to anybody who can shine some light on this :)