Jeremy probably had about three minutes (between 3:31 am and 3:34 am) to get dressed, if his account is correct, whilst he decided whether to call the police. That left him about a minute and a half to find the police telephone number(s), possibly try to telephone Witham police station, and telephone Chelmsford police station. Pc West then logs his call at 3:36 am. It's certainly possible to get dressed in three minutes. Some boarding schools would require a pupil to do that (including a brief wash) on occasion as a form of minor punishment.
Morning Reader

It's impossible that the call was at 3:36 its more likely that the call ended at 3:36 and it was more likely the call was made at 3:26 and this I believe was excepted at the COA.
PC Cracknell stated in his statement that due to a call to the information room at 3:33 he headed of for WHF.
Plus car7 or was it 5 was called out at 3:35....
Jeremy arrived at WHF at 3:50
The drive to WHF is just under 8 minutes, so he had a possible 8 minutes to get dressed, lock up and get into the car.
Of course he could not have called Julie at 3:30 because he was still on the phone to police; which makes it more likely that he called Julie first, after the call to Witham. This is the call that we tend to forget he made, although there is no proof he made that call, but he must have done to know that the station was not manned.
