A closely-fought game swung back into the visitors favour as Brooks, Harris and Killey all netted.
Haroldeans chief Fraser Saville wants his side to mount a cup challenge after giving up the ghost in the MJSL.
He said: "We should be concentrating on the cup as it looks like we can’t win the league now.
"Everyone will continue to give their all, but we know we can target this competition. There is no reason why we cannot go all the way.
"We face Reich Insurance Rovers in the next round. If we progress, then you never know."
Report by Darren Witcoop