It's a must add @richard.spicer.7906 I was lucky as this was already established in the back garden when we moved in. Such a great plant & amazing deep purple colour. I was one of the few plants/shrubs I made sure was left alone.
I have one Buddleja in the 'wild' part of my garden that has never flowered (I need to move it or take cuttings) and I've always wondered if it will surprise me. The others I have are lilac, pink and white. Plus globosa too which was my latest purchase.