I travel past this place on a regular basis with work, and have noticed that the former BBC Pebble Mill site is still empty, I know it's a dream that will never happen, but wouldn't it be great if the City Council bought this land for the Nature Centre to enlarge the place.
As it is it's getting some interesting additions to it's collection and showing them in a good way despite a lack of space to expand. Another option would be to take some space on the other side of the site in Cannon Hill Park.
I wonder what the long term plans are for the park regardins lack of space and bringing in new displays.