Neither were asleep. Nevill would have been downstairs in the kitchen after having returned from his usual nightly walk with the dogs. Not forgetting that Nevill had continued working on the rape harvest after Jeremy had left .
As a force of habit, Nevill would then have sat with a G&T and a smoke to unwind before having a shower and also waiting for June to settle as she'd been a poor sleeper.
June would have been in bed but not necessarily asleep as it was obvious that she'd been reading the Bible.
Two teacups were found downstairs so either June and Nevill had a drink each or Nevill and Sheila may have had as at some point Sheila also had a snack late on.
It would have been quite late at this juncture and perhaps only another 4 hours before Nevill would have been up again to begin another day of harvesting, so whatever happened between midnight and 3am nobody will ever know and it's futile to even speculate.
We can look at the evidence and speculate.
If Jeremy is innocent, that means something happened around 3 a.m. or so (we can only go roughly on times). Would Nevill and June normally still be awake at that sort of time? Would Nevill be drinking into the early hours of the morning? He didn't have a drink problem that I'm aware of. It seems unlikely to me.
However, I don't believe they were asleep. To that extent, I agree with you. It does seem more likely that at least June was in bed and something had roused her, and she then sat up, or maybe sat at the edge of the bed. Nevill was out of bed already. He must have been. Look at the bed sheets.
I understand why there is a need for the rifle to have the silencer on it. Jeremy might have anticipated that the report would alert the adults to his presence. But to me, it looks like the rifle didn't have the silencer on it. Otherwise, why are they awake? How is Nevill downstairs in the kitchen? Even if we think Jeremy did it, why can't we admit that it is possible that Sheila is the killer and she just went on a rampage?
The struggle in the kitchen also points to Sheila, because Nevill would be hesitant in dealing with his daughter. Jeremy and Nevill would not enter into a struggle in the kitchen. Jeremy was armed and would just kill him in the bedroom or, if he ran out of ammunition, he would tackle him on the stairs or upstairs.
People laugh at the idea that Sheila stopped to wash herself, but if we believe the Crown's case, then we must accept that:
(i). Jeremy killed his own family for money.
(ii). Jeremy entered and left the house through a narrow casement window without leaving any blood traces.
(iii). Jeremy carried out the massacre without leaving any direct forensic evidence that he had done so.
(iv). Jeremy nevertheless implicated himself circumstantially by leaving a bloodied and 'sticky' silencer in the gun cupboard.
(v). Jeremy also very kindly stopped during the massacre to scratch the aga surround so that the silencer would have further incriminating forensic traces on it. Thanks Jeremy.
(vi). It was helpful of Sheila to stay asleep all the way through it all. Everybody else involved in this case is a light sleeper and some of them get up for 3 a.m. phone calls like rabbits on Duracel, but not Sheila. That lass slept like a log.
(vii). Former Scotland Yard C11 Branch detective Stan Jones regarded Jeremy as prime suspect from the off. This same Stan Jones offered Jeremy the keys to the crime scene, and left all the guns in the house for Jeremy to find. That was nice of Stan Jones, given that Jeremy was a suspected mass murderer.
(viii). Jeremy declined this open goal and was delighted that the relatives were given the keys so that they could find a key piece of evidence that Jeremy had left there.
(ix). Alternatively, Jeremy broke into the house later and left the evidence there for the relatives to find - which was very nice of him.
(x). It was also very considerate of Jeremy not to leave blood in the den, in the gun cupboard or in the cardboard box in which David Boutflour found the silencer. Leaving the place spick and span shows that Jeremy was not just a mass murderer, but a mature and responsible young man.
(xi). Jeremy tells his girlfriend, Julie, everything. Jeremy then splits up with her. I suppose as a former public school boy imbued with the English traditions of amateurism and sportsman-like behaviour, Jeremy was doing his best to help the relatives and the police put him in the frame. It just wouldn't be cricket otherwise.
(xii). We are to believe that Julie was not an accomplice and was not arrested, instead she went to the police voluntarily, but only after more than a month, during which time she slept with Jeremy, socialised with him, and identified all the bodies because she thought she could talk to the dead.
But let's say Jeremy is the killer. I think he didn't plan it. He was psychotic and over-estimated the lethality of the murder weapon. He assumed it would all be over quick, and instead it got messy and he was left to improvise. He comes up with the phone call alibi idea after Nevill ends up downstairs. He recalls a genuine call that I would speculate Nevill made to Jeremy earlier in the evening, which started it all off, in which Nevill berated him and Jeremy thinks that he can fake a call. He doesn't give much thought to it beyond leaving the rifle on or near Sheila's body and he then ropes in Julie by ringing her in the early hours of the morning.
The difficulty with that theory is the 3 a.m. phone call (or 3.15 a.m. or whatever time it was). Isn't it quite a coincidence that Julie is there to answer the phone herself?
It's convenient that Jeremy eventually answers the phone for Nevil, but that's not a coincidence. Jeremy can explain this away by pointing out that he is Nevill's son, Nevill wants to contain problems in the family and not involve the authorities, blah, blah, blah and so on. Nevill is at a stand-off in the kitchen with Sheila, who is carrying on and has the loaded rifle that Jeremy left out earlier. Nevill assumes she won't use the rifle, but he doesn't try to tackle her, maybe because he can't catch her or whatever reason. Nevill waits for Jeremy to answer the phone. The phone has a loud ring. Eventually Jeremy wakes and answers, etc., etc., and so on. Make of that what you will, but it is plausible.
But then Jeremy rings Julie, and she answers too - a handy coincidence.