All I can offer is this, of a 103 Sqn crew circa early 1942. There are the windows previously mentioned, no sign of a door though.
(The bloke on the far right - a man named Phil Smith - would finish his tour with 103 Sqn, instruct at an OTU for a year and then be shot down on the last trip of his second tour, his 51st all up. He was the only survivor of his crew (a relative of mine was his navigator) and died in 2003.)