Chris Banning, their 19-year-old striker, opened the scoring as they raced to a three-goal lead. However, the English club fought back to level the scores, before late goals from Danny Jones and Ben Selly secured the points.
Malcolm May, the Whitchurch chairman, said: "It's been our driving ambition to get back in the National League. We enjoyed it very much when we were there, except for a few of the results, and we have set our hearts on getting back. We would love to seal our position on Saturday at home to Gloucester."
May said the club's ambitions had been enhanced by the efforts of their new coach, Nazir Mohammed, and the senior internationals, Tyrone Moore and Mark Lewis.
One club who will not be making the ascent to the National League are Bath Buccaneers. Their hopes finally collapsed when they went down 4-3 to Weston-super-Mare. Yet the first distress signals were evident when, at the halfway stage of the competition, they parted company with their player-coach, Ian Jolly.
In the South, Wimbledon, with a goal from David Alford in 36 seconds, beat Richmond 1-0 to take over from the inactive Fareham, whose game at High Wycombe was played as a friendly when one of the umpires failed to arrive. In a scrappy game, Wimbledon were grateful to their goalkeeper, Kelvin King, for a 60th-minute penalty stroke save.
Old Cranleighans, who have had their own difficulties with umpires at Wycombe, with the consequential deduction of three points, moved into third place following their 2-0 win against Winchester.