Needless to say, poor Silvie wasn't for having her ears photographed!
Anyway, we were at the vet today for her booster and I asked him about these spots. he said it could be some kind of allergy or acne based thing. He also said, thankfully, taht it was nothing to worry about if all the spots did was arrive and then leave - I should only worry if they appeared to be bothering her of if they hung around at all. She does get that black stuff under the chin, but only to monor extent, so its probably linked.
I guess I'm happy as long as the vet is and Silvie is! Poor Silvie...