Nevill could have slept in "Sheila´s" room occasionally when there were no visitors. That woud be the reason the bed was made up. Besides Sheila´s things were all over that bed, she used it as storage for her clothes, toiletries and makeup. It didn´t look ready to be slept in.
Do people really think that Jeremy would have slippers in the house - or that he would use Nevill´s?
On the one hand, we are made to believe that Jeremy had a horrible relationship with his parents and Sheila, yet he would be hanging around their house just like that?