We've got a shelving unit we no longer need.  It is the same style and dimensions as this one: http://dwell.co.uk/107246/Porto-six-cube-storage-white/  and is from the same shop (Dwell), but in an oak veneer.  It no longer has the casters, so it sits directly on the floor.  Is a bit rickety to move, but perfectly solid when stationary (we had it full of books and a TV on top) and is otherwise in good condition with no marks, scratches, etc.  We've dismantled it, so you'd need to put it back together, which should be easy enough.