The victory sees Rookie of the Year Smith earn a Challenge Tour card for 2016 alongside Darren Wright, Sam Connor, Howley Hall’s Marcus Armitage and Aaron Rai.
Smith won the Tour Championship on the fourth extra hole having carded a final-round 64, eight under par, to set the 13-under mark which was matched by Midlander Rai (68 68 67) and Gavins (67 65 71).
Gavins had needed victory to edge Gary King out of the Challenge Tour positions.
He had been unwell during his last two rounds and dropped out of the play-off on the third extra hole when he bogeyed the par-four 18th.
Rai’s approach at the next found greenside water and he was forced to take a penalty drop while Smith held his nerve to make par and land himself promotion to the Challenge Tour in his first season as a professional.
“I am over the moon,” said Smith, who takes home a new Motocaddy trolley, Bushnell Tour X Range Finder, Bolle Sunglasses and £500 to spend with HotelPlanner.com as well as the £20,000 winner’s cheque. “It was tough, I am mentally and physically drained but I am delighted.
“Winning the Order of Merit is the icing on the cake and I am looking forward to playing the Challenge Tour now. My target for the season was to get a win so to get another is above and beyond what I was expecting.”
Gavins, who led by four overnight, surrendered shots at holes two and four in his round, but birdied six, 12 and 17 for his closing one-under-par 71.
Malton & Norton’s Chris Halley (72 76 68) and Middlesbrough’s Michael Skelton (74 71 71) tied for 33rd place.
Halley closed with a flawless round, which included birdies at holes one, seven, eight and 17.
Skelton’s 71 was remarkable as he dipped below par despite shedding five shots in his opening two holes – four of them at the first.
He then had four birdies in a row and closed the outward nine with an eagle 3.
After all the fireworks he returned home in par, with two birdies and two bogeys.
Hornsea’s Steve Uzzell finished equal 37th (71 72 74). He had three birdies in his opening four holes – as well as a bogey on the second.
He also had bogeys at the eighth, 12th, 15th and 16th plus a double-bogey at the 10th, birdies at the 13th and 14th offering some compensation.
Rotherham’s David Booth tied 50th, bettering his opening 82 on the final day by 14 shots.
After his second-round 76, which included a 10 at the 437-yard par-4 11th hole, he carded a 68 that included a run of four birdies in six holes from the turn.
Armitage, twice a winner this season and second in the order of Merit going into the event, placed 53rd (78 75 76) after a disappointing week.
He double-bogeyed the first but retrieved the shots quickly with birdies at the second and third holes.
He had three more bogeys and one birdie to the turn and then cam home in two over (four bogeys, two birdies).
Doncaster’s Graeme Clark finished 55th (77 74 87), his calamitous final round including three birdies, but also one quadruple bogey, two triples bogeys and three double bogeys.
Highlights of the Matchroom Sport Tour Championship air on Sky Sports on Tuesday, November 10 with a HotelPlanner.com PGA EuroPro Tour season review show to be broadcast seven days later.