It's all too subjective. Was the neighbouring property even occupied? Perhaps they were on hol or working a night shift. Maybe deep sleepers and/or wore ear plugs. Perhaps the party wall was thick.
We use the word 'subjective' differently methinks.
Anyway, I have since solved the problem, replacing it with a lesser problem. The time Bamber gave for Nevill's call had to be earlier than the time at which he called Julie and he could not be sure no one at Julie's place would note the time precisely. Now, the problem is: why did he call Julie shortly after 3.00 a.m? (see below)
The times are hopelessly unreliable with most of the witnesses changing their times. When I have time I will go through the WS's and plot the witnesses with their times on a timeline coz I'm sad like that 
It's a good thing to be sad about. Let me help. Bamber said Nevill called at three. He was wearing his watch (Ann Eaton). He has since moved that to '3.15 or 3.30' per his recorded interview from prison which Myster, I think, posted recently.
In the 2002 appeal, the judge summarised the evidence of Julie's roommates on the time of the call to her as follows:
Helen Eaton 3.00 (but at trial she agreed in cross it might have been 3.30)
Sue Battersby 3.02 (after adjustment as she kept her clock 10 minutes fast)
Joanna Wood 2.00 - 2.59 (she only remembered it was a number beginning with 2)
Julie Mugford 3.30, corrected to 3.15 after calling someone at her place (source, Ann Eaton)
Julie's timing should be discarded as she was (IMO) complicit in the crime. The others tend towards 3.00 a.m. which is also the time Bamber assigns to Nevill's call. It rather looks as though he was obliged to say Nevill called at 3.00 because he placed a call through to Julie right after.
