I have just had the opportunity to take some photographs of what used to be the most biodiverse roundabout in Bracknell, the Sports Centre Roundabout. Just before Christmas I reported that there had been a large number of trees and shrubs felled, many of them native, reducing what was a very heterogeneous habitat to a much more uniform one. You can see the before and after pictures below.
It is a shame that it is winter and that the leaves have fallen, but I think that you can get the picture. it is particularly sad as we have recently published a paper showing that native trees are particularly useful on roundabouts for both insects and birds (Helden et al., 2012).
Helden, A. J., Stamp, G. C. &Leather, S. R. (2012). Urban biodiversity: comparison of insect assemblages on native and non-native trees. . Urban Ecosystems 15: 611-624. http://www.harper-adams.ac.uk/staff/profile/files/uploaded/Helden&Leather2004.pdf