Most regions of the UK are bound to have a specialist vehicle paint supplier. They will be used to supplying specialist paints for classic cars etc and will normally be able to provide the paint in aerosol cans, usually while you wait.
If you can take a section showing the current faded paint they should be able to match it. The code numbers will obviously help. The CAMO, by the way, only ensures that any work done on the aeroplane is permissible, done correctly and also properly recorded. Its unlikely that touch ups will require much if any paperwork but you can consult the CAMO, of course, to be on the safe side. Make sure that all corrosion is removed and the bare metal is then etch primed or you will be doing it all again in not too long henceforth.