After a first half which was as disappointing as most of April had been, Welling put in a second period display that finished their season in spectacular style.
Although they took an early lead, Welling conceded three first half goals and looked dead and buried.
Some harsh talking at half time galvanised them into a second half performance that earned them a final day victory to take them to 60 points.
It took just ten minutes for Welling to go ahead. Harry Beautyman’s corner was only half cleared and Ross Lafayette picked his spot with a crisp volley.
Five minutes later, Southport were level when Luke George’s shot took a deflection giving Lee Butcher no chance.
Vinny Mukendi then put the visitors ahead when Osayamen Osawe’s shot rebounded out kindly for him.
Manager Jamie Day chose to give Jake Gallagher the attacking midfield role with Josh Wakefield took the position in front of the back four and it almost paid dividends when Gallagher lifted the ball over Toto Nsiala before snatching at his shot and sending it wide.
John O’Sullivan then put the Sandgrounders further ahead with a shot from the edge of the penalty area after excellent work by Mukendi.
Gallagher and Tobi Sho-Silva combined to give Joe Healy a chance but his volley was saved by Danny Hurst.
Just before half-time, Sho-Silva’s cross was flicked on by Lafayette but Gallagher, stretching, was unable to guide an effort on target.
Three minutes into the second period, Welling reduced the arrears.
A foul on Lafayette on the edge of the area was punished to the full when Beautyman’s brilliant free-kick flew beyond Hurst into the back of the net.
Lafayette thought he had equalised when he met Healy’s header back from Beautyman’s corner with a firm header but Hurst flew across goal to tip over spectacularly.
Hurst again came to Southport’s rescue when Healy’s excellent through ball gave Sho-Silva a chance but the Sandgrounders’ goalkeeper kept his attempt to round him out with his legs.
He was given no chance when another scrumptious Healy through ball was lifted over him by Gallagher into the roof of the net.
Another brilliant Hurst save stopped Gallagher from putting Welling ahead after Sho-Silva pulled back Tom Bender’s long throw then Blaine Hudson hooked over after a corner was knocked behind him.
Bender’s long throw evaded all but Beautyman was unable to bundle home before Welling went back ahead.
Nsiala handled in the area, and after being cautioned, watched on as Lafayette sent Hurst the wrong way from the spot.
Nsiala was then dismissed for his for a second booking following his part in a skirmish following a nasty tackle on Bender by John Dillon.
Substitute Toby Ajala was then foiled by the quick thinking of Hurst, and the Southport goalkeeper did well again when blocking Loui Fazakerley’s effort as he was sent through by Ajala.
Quade Taylor shot wide in his final game for the Wings on loan from Crystal Palace but Welling held on to claim a sixteenth place finish in their first season back in the top division of non league football.
Welling United: Butcher, Fazakerley, Bender (Obersteller 85), Wakefield, Taylor, Hudson, Beautyman, Gallagher, Sho-Silva (Ajala 80), Lafayette, Healy (Karagiannis 87). Unused substitute: Day, Turner.