I had half an hour inside the BBMF Lanc at Fairford in 2010 and took a lot of photos of the interior. Should anyone want copies PM me. Or if someone knows the system for posting them on PPrune also let me know.
The men who flew Lancs were much braver than me. A very long and difficult route to the exits for most of the crew.
p.s. The only armour I could see was the pilot's seat back. Certainly none in the turrets.
Don't know why you guys are arguing about Lanc vs B17. Totally different mission configurations. Both great aircraft.