TfL Press Office just rang me about this one. They sounded a little surprised themselves to find a docking station had been installed where access was restricted by stairs (I believe 5 steps in total).
The press office have since looked into it and have been informed by the docking station planners that at this stage the stair situation with Southwark Tube docking station is a one-off. They are also interested in gaining some feedback from anyone that has tried the new docking station and how they found dealing with the stairs.
This thread is being watched by TfL so please post your constructive comments on the Southwark Tube docking station below.