We went to Magna in Rotherham this week. It is built inside a former steelworks. The outdoor playground was great (apart from the view of an ugly steelworks and the strong smell of garbage from the neighbouring recycling plant), but the science centre was really awful. There is no natural light and not much electric light. It's creepy and looked like it was designed by the makers of horror films not scientists. There were a couple of small 'hands on' areas, but the atmosphere is so dark, noisy (constant furnace/steelworks sound effects) and unpleasant that it was impossible to stay there very long or to learn anything.
Bizarrely a couple of people had told us that it was good there, but I guess they were talking about the outdoor play area.