Peacehaven needed extra time to get past hosts Mile Oak 4-2 in the John O'Hara League Cup third round.
Dave Wade put Oaks ahead from the penalty spot but Peacehaven levelled from their own penalty via Matt Balmer before further goals from the hosts Neil Roberts and visitors John Donoghue sent the game in to extra time.
Dan Hamilton and Donoghue then netted to secure Peacehaven's passage.
Peacehaven assistant manager Jim Thompson said: "We are just pleased to get through although I felt we made hard work of it."
Selsey came from behind to beat Hassocks 2-1. Pat Harding fired Hassocks ahead midway through the first half but Selsey levelled when Jason Reed headed home Jon Bines' cross and Ian Ford pounced for the winner on 70 minutes.
Boss Danny Hinshelwood said: "You have to give credit to both sides and the referee for making such a good game of it in those conditions."
Withdean 2000 consolidated third place in the Combined Counties League with an impressive 3-1 win at Southall.
Sam Francis headed home his 26th goal of the season from a Rod Davies cross to put Withdean ahead early in the second half.
Andre Robinson levelled for the hosts but Ollie Rowland restored the lead after a Francis shot was blocked and Justin Simmons wrapped up victory with a wonderful goal, scoring from the halfway line with a shot which bounced over the keeper's head.
General manager Mark Stevens said: "Last week Southall beat Ash, who are top of the league, so this is a very good result."
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