Posted: 11/02/2014 at 08:47
Simon, cut the buddleias down to knee height about now and give them a sprinkling of Fish Blood and Bone and you'll be well rewarded.
How close to the conservatory is the one you're worried about?
In 50+ years of gardening I've never met a garden buddleia whose roots damaged a building.
The only ones I know that have done that are the ones that grow from seeds blown in the wind which take root in cracks in mortar and on rooftops.