The door to the car park may be just for bringing in the stock to avoid having to take it through the front entrance and to give an emergency escape.
Update: There’s a ‘beer garden’ on the car park side with access through the snug lounge. It’s not complete, yet, and on the day I looked it was raining heavily so no customers.
On the other side of the station, I passed an open double door behind the Heras fencing where contractors were installing what looked like support steelwork for wall panels but the heavy rain made me hurry past!