Good idea.
My 11 reasons/facts go together with the substantial evidence already written on this thread.
Jeremy being awake at 3.00am has good & bad points.
Good points -
He is more likely to answer the phone before the answering machine came on. Neville would have been unlikely to wait several minutes for an answer if the answering machine was off.
Bad points -
Jeremy was awake and rang Julie before Neville rang. According to Julie, Jeremy already knew there was something wrong at the farm, he had not slept all night & everything was going well. Jeremy did not refute this to the police, saying 'no comment' when asked why he phoned Julie. If Jeremy knew these things at 3.00am, he must be the murderer.
Jeremy lied to the police, saying Nevilles call woke him up. He then lied to the police saying he phoned Julie after the police.