"Jupiter" wrote in message
I'd have a close look around the base of the shrub to make sure that the
shoots with the mauve flowers are actually coming from the main
shrub.

Yes , they are. The branches some carrying white and some carrying mauve
flowers are high in the air and all growing from the same 'trunks' of the
same buddleja.
It's an interesting and pretty affect that I had not seen before on Buddleja
davidii.

Anthony