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is the backup stored somwhere else other than the games folder as i have deleted every thing but the image files and redownloaded the game and the mods

Your issue has happened to me several times. Its problem lies in the backup folder. Make a clean extract of the game and place the 'randomportraits' folder inside the mods folder. Only then launch the game for the first time and apply the mod following the modding guide. The game will close, now you have to delete the backup folder (inside game folder) before doing anything else. Finally launch the game and confirm that the mod is applied and the game is working.

I take it that the problem is the backup like to correct 'mistakes' that the mod has introduced. Do i need to deletee the backup folder everytime? or just the once?

Im not entirely sure but I think just once should do. 

You need to extract the game fresh.  The problem was that the old version would backup already modified files, potentially broken files,  then use those files. Some versions also didn't replace the back'ed up files with the new files so it'd potentially intermix versions.

Extract a fresh copy of the game, the entire game to a fresh folder,  don't mess with the backup folder. Run it, then click apply for mods.