Following on from a comment in the 'boundary' thread I thought I would share the link for the FC map viewer.
http://maps.forestry.gov.uk/imf/imf.jsp ... wales_ext&
Although this is the Welsh version, I know that there is an equivalent one for Scotland, so presumably for England too.
I use it all the time. We can switch between aerial photos taken in 2006 and then 2009 which has been invaluable for us because our woods was clearfelled around 2002 so we can see how things have progressed and, more importantly, where the drainage ditches are under all the brambles. The measuring tools have been brilliant when planning where to put in the tracks. I can do it all virtually, work out the length of track and calculate the area of each cant created.