Buddleia Flower Power.

We don't have that particular one Woo but we have 3 others in various areas although all are in full bloom at the moment if I had to say which was doing better then it would have to be the one in partial shade.

But you know me....don't take my word and wait for an expert!!

 

Well I don't have any buddleia, and I'm no expert but where I used to work many years ago they grew like weeds in the yard, it was a builders yard so full of all kinds of rubbish.
I did read once that I think it was introduced to this country from China (ring any bells ), and spread by seed along railways, it liked growing in the shingle.

Bearing that long winded idea in mind I would go for the Saharan side of the garden.

 

Flower Power is a synonym of Buddleja X 'Bicolor', a seedling of B. X weyeriana. It's quite tough, but certainly no weed. The soil needs to be both well-drained and moisture retentive, as these hybrids are not completely drought tolerant. They are also heavy feeders.
I would suggest the full sun position, but incorporate plenty of organic matter into the soil first, and then ensure the soil never dries out – at least for its first year. Add a little lime if your soil is acid or if there aren't plenty of earthworms. Feed and mulch in spring when you prune it.