Uckfield sealed the Sussex One title with a 46-5 defeat of Rye and are on course to finish the league season undefeated.
Coach Geoff Atkinson and assistant Chris Burton are now aiming to establish their team in London Four South East next season.
Skipper Phil Rowland ran 80 yards for the opening try and was followed over by man-of-the-match Gustav Smook, who went on to complete a hat-trick.
Leigh Bialik converted his own try with Nick Ridley (2) and Joe Feldman also going over.
Hastings and Bexhill need two wins from three games to ensure second place after Rob Sparks' try and a conversion and penalty from Paul Sandeman clinched a 10-5 home win over Crowborough.
Seaford can still snatch the runners-up spot but they did themselves no favours by losing 16-15 at home to Pulborough.
They wasted 24 points in missed goal kicks which meant tries from James Anderson, Ben Cox and Kevin Woodward were not enough. Toby Steele crossed for Pulborough and Dave Elly added two penalties before Jon Scrase grabbed the decisive score.
UC Chichester beat Hellingly 40-3.
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