If Sheila was in the main bedroom that night, I think she would have been there to sleep - either because June was worried about her (as per the call to Pam) or she wanted to be nearer the twins. I find it hard to believe there was any 'bible reading' and if she did sleep there, it was simply for convenience.
This is a response to Susan's post.
There is no suggestion here from Caroline that Neville was in another bedroom.
Caroline has informed me today (weeks later) Neville was supposed to be in another room.