After starting brightly, they somehow found themselves 2-0 down with 15 minutes gone at the Tithe Farm Social Club.
They responded strongly, with Ben Acey and a penalty from Matt Loaring drawing them level in the second half.
But against the run of play, the home side got the winner five minutes from time.
A Callum Webb shot beat the goalkeeper only to find the post, but the rebound was tapped into the empty net by Elliott Buchanen.
The Green Lions are at home to mid-table Uxbridge on Wednesday night with the kick-off at 19:45.
They remain second from bottom in the Isthmian South Central.