crocus, could you post a photo of the base of the plant and maybe a closer view of the seedpods?

Buddleja davidii?

crocus74 - was this a wild plant or from a garden? And what part of the country? Judging by the lovely rock, not central London ;-)

And was it in uplands, lowlands, wet, dry?
Was it on an actual shrub, or a perennial plant which had died down for the winter?

I don't think it's Buddleja. The extra pictures of the base and a close up would also help.

Did it look like this?

Here is a link that might be useful: Spiraea douglasii