There are three car parks at Sevenoaks, one immediately at the rear of the station which I *believe* is (or certainly was) for season ticket holders only on weekdays. The larger one is on the other side of London Road, with vehicular access via Morewood Close round the back of the Fire Station and Lidl. The third one is a smaller one at the front of station for short stay only. From what I've seen in recent months, you certainly shouldn't have any difficulty finding a space in the main one across the road. Failing that, there's a council multi-storey off Bradbourne Park Road a few minutes walk from the station, which always seems to have spaces as well.