I haven't taken it out for a couple of months, but the headlight worked last time I used it.  The high and the low are both not working, so I don't think it's burned out the filament.  All the other lights are working.  Any ideas on what I should do?

Why do you believe light bulb isn't blown ... cos they blow often.
Pull the plug off and test voltage at the plug I guess.

Hold all the "How many gstwinners does it take to change the light bulb jokes" for now please.

Cool.
Buddha.