I'm not a buddleia expert, but, I think the butterfly bush pruning rules apply mainly to cold, continental type climates, where a late freeze in May could stunt its ability to successfully make new growth for the duration of the growing season. I don't think it gets that cold in London, does it? I'm under the impression that all of Britain has a fairly mild climate, thanks to the Gulf Stream. I live in a mild climate (except for the hot, humid summers) and mine hold most of their leaves all winter long - I prune mine to about 2 ft. - 3 ft. tall in early spring. If yours has grown 10 ft. tall, then you must be getting enough heat for good growth. I say, go ahead and prune it, it'll probably do it good, make it bloom more, which is what you really want. It's your garden, and if it's blocking much-needed UK light, then it needs a trim! Sherry

I cut mine back to about 2' tall in early spring and leave them alone the rest of the year, except to cut the spent flowers (deadhead them) to keep the blooms coming. Occasionally, I'll cut back a "stick out" branch later in the year or a branch that's covering another smaller plant nearby - most butterfly bushes are very vigorous. Pruning revitalizes them, so don't be hesitant to do it. MissSherry

I would think you could just prune it back a little bit to stimulate fuller growth without sacraficing size much. Even a more drastic pruning won't necessarily result in a smaller bush. Every other year or so I hard prune my Abelia and they return the same size they were, just fuller. The same seems to be true of butterfly bushes, but I don't have any mature ones to say for sure. Somehow the one I planted for my mother sprang to full size in two years while mine are still half the size. She has better sun, I blame it on that. Anyways, I think pruning it by up to half will result in a prettier bush with more blooms that I doubt will be any smaller. At the same time, it won't hurt it to leave it alone for another year either. -Ais.

There's another choice that was given to me. I was told to let it grow wildly for 3 years. Then, I could pick the 3 strongest stems/branches, prune out the rest and prune up the chosen ones. I'd have a Buddleia tree. Now, mine are huge and flop, too. I'm planning to move them as soon as the weather frosts, but I'm going to try the tree thing. Maybe. Since I'm moving them out to the side of my property as a wind block, I might just stake them up and let them go! Love these babies. They make your yard wiggle with life! Christine