Ilsington started the brighter, taking the game to Kingskerwell and creating many problems for the visiting defence.
The pressure reaped dividends when Harper outpaced the left back and cut inside before unleashing a thunderous shot which the keeper could not hold and Lacey was on hand to stab the ball into the empty net.
This visitors were awarded a penalty when Jamie McGuinness commited a foul inside the area, but keeper Kevin Powell saved the resulting spot-kick.
Minutes later a Colwill mistake gifted the ball to the Kerswell attack and the scores were level.
The half ended with the hosts having several chances, the best falling to Lacey, who made no mistake in restoring Villa's lead.
The pitch was, by now, pretty cut up and both sides were finding it difficult to get any rhythm going.
Harper made it 3-1 30 minutes into the second half with a fine solo goal.
Kingkerswell pressed forward and forced a number of fine saves from Powell, before Harper again stepped up to the mark, scoring his second of the game with ten minutes of the game left.
Harper was only denied his hat-trick by the heroics of Kingskerswells keeper.
The Jail Ale man of the match was Ilsington's veteran Richard Webb, who is fast approaching his 50th birthday.
Tomorrow, Ilsington Kingskerswell 3rds at home in the league (2.30pm).