This prompted me look at a nearby hedge for eggs the following winter and I found 15. Since that time I have seen at least one or two females every year and about (c.15) eggs. It has been very disappointing not to see any adults in late summer 2012 and zero eggs this winter. I just hope this is a temporary blip and they will return this summer. I will update here as and when I have any more news.
I have included a montage of pictures taken in and around my Somerset garden over this period.