It is quite ridicuolous in an emergency situation to waste time in this manner.
At the moment there are 3 reasons he would phone a police station over 20 miles away. Which all go hand in hand -
He thought it would give him more chance of getting picked up by them from his cottage.
It gives him more time to change/clean after arriving back at his cottage & prior to meeting the police.
If the police could check call times, it justifies a gap of 15-20 minutes after Nevill's call - 'I was looking for the number of Chelmsford Police'.