Advice on priming White Metal needed.

Good day all,

                  Have a set of Aeroclub W/M undercarriage legs for my Hunter Mk.6, got them nicely de-flashed etc, smoothed sanded etc. Very shiny look, would be happy to leave them like that as the undercarriage on Hunters is Aluminium/Chrome anyway, but there are a few kit parts that need to be added on, and they are the usual grey plastic, so the lot will need a paint job. Never seen W/M parts before let alone painted them, what primer would do the job, I have a spray can of Halfords grey auto primer, and a bottle of Xtracolor Matt light grey base coat, (Hannants XDBB) Are either or both of these suitable, or do I need something special ?

Many thanks,

Mick C.