Thx that was good advise! For some reason it was playing up first time round but after I presume a PC Restart that fixed? It managed to work fine and have downloaded and used several mods with minimal issues : >.
Incase anybody else runs into this issue I used the C Drive (where the game is) and created a new Folder outside all the TDU stuff just called "TDU TEST" (But can be named whatever) then put any mod files I downloaded into that folder then Extracted into that folder then for example if there was a Folder like Euro - Bnk - Level - Hawai - Area 0, I'd just make a copy of that folder for a backup (incase of issues) then simply Replace the individual files into the folder to overwrite. Is a bit tedious on bigger mods or if having to use multiple but if it works it works haha.
Just be sure not to forget to BACKUP FILES XD
There maybe a better workaround but that's the best way I could do it. Hopefully this helps anybody else having same issues : >