Lovely paint job Vaughan. As for the
decals if the only problems are the ones I can make out in the photos you've got three choices. You can leave it,markings weathered,one of Marseilles Bf109s famously had chunks of the upper wing Balkenkreuz missing. You can touch up with a fine brush and paint,luckily black and white are the easiest colours to fix. Finally you could get radical,sand the
decals off and so a complete repaint.
Martin not all Ju87s were fitted with sirens. Some had the mounting blanked off,making a nice foot rest.
And others didn't have them at all.
Cheers
Steve