Touch-up paint
I found this touch-up pen in the armrest console. Not wanting to risk uncertain age paint on the car I ordered an aerosol and new touch-up pot from MGOC Spares.
There are quite a few areas of surface rust around the bodywork - mainly along the chrome strips - so they'll definitely get used.
Update - The MGOC paint was not a good match, but I found that Halfords own brand was.