West didn't say how long it took the operator to get back to him.
That's correct. It's possible that the operator "got back to him" almost immediately rather than by calling him back.
This timetable is entirely made up.
It's based on Pc West's evidence at trial, not made up. What you're claiming is that Pc West grossly underestimated the times he gave in his evidence.
Jeremy insisted he spoke to Julie after calling Chelmsford.
That's a misleading simplification of what was stated in Jeremy's interview. Jeremy was saying he couldn't remember, but thought that his original statement would have been correct. If Jeremy attempted to call Witham before calling Chelmsford, that allows his original statement to be interpreted differently. It just happens that Jeremy wasn't asked specifically about that and doesn't seem to remember (at trial ans subsequently) whether he did or didn't try to call Witham.
I know that West estimated he was on the phone for less than a minute before placing Jeremy on hold but his estimate is not credible it would have taken several minutes to record everything he got from Jeremy.
Even so, it's still possible that the four portions of the call took 2 minutes (taking details initially), 2 minutes (passing the details to Bonnett), 1 minute (contacting Witham by radio), and 1 minute (final conversation with Jeremy, asking him to got to WHF and telling him that a police car was on its way).