After a goalless first period, Manor took the lead on 58 minutes through Dan Okah's drive that crept past debutant Joe Carter in 'Side's goal. The strike went through a crowded area and gave the young goalie no chance.
'Side pushed for an equaliser but it never came and defender Jake Brocklebank sealed the win for Manor deep into stoppage-time.
The loss leaves Gus Gulfer's team in 12th place in the league table.
'Side: Joe Carter, George Ademiluyi, Paul Wright, Marvin Birch, Augustus Ruzgas, Dale Lee (George Lutaaya), Jakub Berkowicz, Jason Ajoodha, David Laird, Jason Fontaine, Akwasi Marfo
Subs Not Used: Patrick Campbell, Fionn Glancy, Kobie Ambrose, Connor Mitchell