Storage ideas. More space under stairs and bookcase on wheels

How to create more storage space under the stairs, giving access to even the most inaccessible part of the understairs cupboard while also creating a movable bookcase on 50mm swivel castor wheels to get the maximum amount of storage space from one area. This clever idea involves creating a simple MDF door in the stud wall under the stairs where the plasterboard and studwork are cut out, a timber cupboard door frame is fixed in place and an MDF door is cut to size and hung in the frame. A basic roller catch is fixed to the door and frame to keep the door closed. Help with making an understairs cupboard can be found in our project here: https://www.diydoctor.org.uk/projects/building-under-stairs-cupboard.htm