Printer seems absolutely fine mechnically, prints no problem no jam etc. However the colours have all become very faint, printing red almost become Pink. All the cartridges state they have at least half the volume in them, so it should not be the ink cartridges? im stuck

Are you technical or not if not then follow these steps
1 go back side of printer & open all the screws on back plate & then disconeect all the conections on formatter & controller bord.
2 remove the screws inside the plate also then u see a black box type scaner *** remove the screws two upper end & other two at bottom pull out that unit & remove one screw on plastic casing remove the cover u will see the some plastic glases pls clean them very smothly & refix them as open if u will feel any problem then call me 918808055506.
i think ur problem will remove goood luckkkkkkk ............

What the cartridges state is not important. You have to be sure the are not empty. Did you try replacing them?? Gerrit Jan