I photographed this web on a Hawthorn bush on the other side of the main path from the car park, and it has been identified as possibly Brown-tail moth larvae. When the caterpillars appear they have hairs which can be very irritating, and the web can contain 300 larvae.
Brian Price
I photographed it yesterday too. Browntail caterpillars as you say, there are a couple on the outside of the web here.
My blog: http://mazzaswildside.blogspot.co.uk/
My Flickr page: https://www.flickr.com/photos/124028194@N04/
Found one of these today on my Photinia & remembered this thread. When I googled it for more info & read how potentially irritating it can be I made the decision to destroy it. Was sorry to do so but I have asthma & a curious nearly four year old who is always helping me in the garden!
2013 photos & vids here
eff37 on Flickr