I don't know if this as already been posted but I found a nice site on the lancs county council website, its called mario viewer and you can look at new and old maps, aeriel photos including 1940's photos of all lancashire, I have just been looking at 1940 photos of Oswaldtwistle, my house was a field then, I have placed the link below, this is ten times better than google earth as it only concentrates on Lancs, again apologies if you are already aware of this site.
http://mario.lancashire.gov.uk/