In a tight game between two sides in the lower-half of the table, the game burst into life with three goals in the final ten minutes.
Forest took the lead through Nikko Stokes on 80 minutes. The lead was doubled eight minutes later when Mohammed Sagaf doubled the lead from the penalty-spot, to put the game out of reach for the hosts.
Michael Ogboin scored 'Side's consolation, a penalty, deep into second-half injury-time.
The result leaves 'Side 13th in the ESL league standings.
'Side are back in action on Saturday when they host promotion-hunting Great Wakering Rovers. Kick-off's at 3pm
‘Side: Wilkinson Boateng, Kyron Richards, Bradley Gayer, David Etcheri, Euan Taylor-Reid, Best Toke (Michael Sherwood), Mattheus Santos, Bradley Joseph, Michael Ogboin, Tony Cookey (Roddy Lemba), Ben Clarke (Jayden Mitchell-Brown)
Sub Not Used: Dean Bouho