Maybe I can add a little extra.
I quizzed my friendly neighbourhood aerodynamicist boffin on this. As has already been mentioned, he agreed that the strakes were fitted to reduce the oscilliatory behaviour in yaw brought about by the differences in the JP Mk 5 front fuse. To quote: "At high incidence a conical body (like a front fuselage) can develop vortices that shed asymmetrically causing large oscillatory yawing moments. The strakes are there to 'fix' the vortices to eliminate oscillatory behaviour." He's normally right about these things and he convinced me.
Hope that helps.
WUT