Hi
We grow and sell a wide range of shrubs and trees bare-rooted. We used to sell buddleia that way (we stopped for commercial reasons to concentrate on hedging plants such as beech, yew, box, hornbeam etc). They move perfectly well - just dig a few up any time between now and the end of February, try and keep a bit of soil around the roots. When you plant them, cut the top back HARD. They regrow anyway, and you reduce the strain on the root system.
Hope this helps
Julian
Ashridge Trees