Yes but if he is lying and knows the calls cannot be traced and the police cannot check if calls were even made why does he create the time delay and cast huge suspicion on himself?
This is a fair point but it's possible he never even thought of phone records until later, he doesn't create the time delay until he is arrested. He doesn't tell PC West he was faffing around for 10 or 15 minutes and in his WS on the 8th Aug he says he tried to call WHF a couple of times and then "immediately" called the police.
You can make allowances and say well, he really didn't know what to do and he was embarrassed to mention his dithering at first but for me, it's then what he does and doesn't say to Julie that really makes this all very suspicious. Why would you wake up your GF in the middle of the night and not tell her that Sheila had a gun? Even worse, why would you not tell her that you had called the police and had to go and meet them?