This seems to be the buzz at the moment in web news and blogs.

CIRIA have just published their guide Building Greener:

Green roofs and walls are widely used in many countries to provide a range of benefits for the built environment. Numerous studies have been carried out to monitor and assess the effectiveness of green roofs and green walls in the areas of biodiversity, stormwater management and climate change mitigation and adaptation.

Meanwhile HOK Green BIM have posted a directory of Green Roofs, including  Carlisle Roofing here in the NW and the informative  Green Roof Directory