Had a good look round this site yesterday, after it had calmed down, picking places I could think of. Obviously a vast on-going project as few if any of the photos so far are later than the 1920s. Over 16000 images online so far. No N Wales slate yet - but I'm sure there's some to come As I know Aerofilms did pics of Votty, Cwmorthin etc.
Worth registering so you can zoom the images - they are obviously scanned at what looks like full resolution. Most impressive - found one of Hulton Ironworks near Bolton - you can see the self-propelled steam cranes, which I remember from over 30 years later (allbeit with cabs)! Sadly I never photographed one.
A good site worth keeping an eye on.
Grahami
The map is the territory - especially in chain scale.