Not sure how Nevill was shot 4 times upstairs.
He died after his call to either Jeremy or the police. Both calls being in the kitchen.
Why would Nevill run upstairs or be marched upstairs by Sheila's accomplice after making one of these phone calls ?
There are also big time constraints after Nevill phoned Chelmsford police at 3.26/36am. To go upstairs, get shot 4 times, go downstairs, fight, get shot another 4 times, get his back burnt, get put on a goal scuttle, then Sheila's accomplice to escape, before the police arrive is amazing.