Sidley dumped out of cup
The Blues made a bright start to the second round tie with Kevin Rose opening the scoring after 15 minutes.
Lancing got back into the game midway through the first half when Jamie Cole equalised.
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Hide AdUnited came out for the second half determined to make their superiority count, but failed to take their chances.
The visitors claimed what proved to be the winner on the hour mark when Neil Richardson headed home from an Andy Long cross.