Earlier, United worked their way to 144-4 from their 20 overs, with the top order of Stu Mosen (26), Brad Watson (22), Zeb Small (36) and Alan Kenny (28) all contributing, as Small and Kenny put on 48 runs in 31 balls through the middle stages.
Wilson was very economical with his bowling, getting 1-15 with one maiden from his four overs.
In reply, Marton slumped to 33-4 and then 40-5, with United bowler Steve Meredith (2-21) trapping both openers Josh Trillo and Ballam Singh LBW for ducks, while leading hopes in both the Dans - Ford and Gordon - were dismissed by Robert Morgan (2-29).
Oliver said they struggled with the ball swinging both ways from United's veteran bowlers.
John Anthony (15) worked to salvage the chase with Rayner after Oliver was run out, but when he and then Dane Slako went, the trophy seemed to be slipping away.
But the excitement of Twenty20 is that the momentum can swing in just a couple of overs, and Wilson hit three boundaries and a six while Rayner got two of each to see their team home.
Marton, who had a tough run over New Year in the 50-over format, finished the Twenty20 competition undefeated to lift the silverware.
In the playoff for third at the Wanganui Collegiate grounds, the college 1st XI upset the Property Brokers United 1st XI by 15 runs.
Reaching 143-8 and Harry Unsworth top scoring with 35, Collegiate restricted United to 128-5, with Josh Lennox taking 3-14 from his four overs, including getting both the United dangermen, Robbie Power (37) and Gerard Hobbs (35).
When Hobbs fell at 81-1 in the 11th over, United could only manage 14 runs from the next 25 balls before Power went, with Ritesh Verma (11) and Brendon Walker (16) then put under pressure.
Nick O'Leary bowled Walker for 16 with three balls left to ensure United could not slog the remaining runs needed.