Thanks for your reply @Russdl
hmmmm - only thing is, these stains don’t wash off. Have tried pressure washing on the fan setting and also used brick acid which removes tannin drip stains on the render caused by our oak frame porch, but not these stains from the cladding.
I would be happy (delighted in fact!) to just sit back and wait if I felt confident the situation will resolve itself, but am not feeling confident about that approach at the moment.
@Russdl - if you have photos or spec for your drip flashing that would be great.
Thanks so much for your time.