All the goals came in the opening 45 minutes.
The home side went ahead after a corner saw Jerome Eccleston rise unchallenged to head home.
The Saints were soon level though when Jake Cass`s free-kick went over the wall and past Town `keeper Jamie Norris.
But the hosts restored their lead midway through the half when another corner fell to Eccleston whose blocked shot fell kindly for Aaron Morgan to fire home.
It was 3-1 soon afterwards with a goal worthy of winning any tie from Charlie Lossaso, who fired in a direct free-kick from fully 40 yards past Saints` keeper Carl Dennison.
Beaconsfield Town's reward is a home tie with league rivals Marlow.
Written by Steve Whitney
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