Southwick have been relegated from division one following defeat at fellow strugglers Burgess Hill.
A seven-wicket reverse means Mark O'Keefe's side finish eighth and go down.
O'Keefe now faces a struggle to keep his side together. He said: "Most players are still enjoying their cricket and are happy to play in the second division.
"But a couple of players have had a taste of the big time and they want to play against the top sides every week.
"Hopefully, I can persuade them otherwise because we have risen through the leagues very quickly with three promotions in four years. I think division two cricket is what Southwick should be playing at present."
Southwick may get a reprieve because the Sussex League need another team.
Laurie Claydon, the Invitation League's competitions secretary, said: "On the face of it Southwick will go down but the Sussex League have a vacancy and they will fill it from either the East Sussex League or the Invitation."
Southwick made 201-4 with Steve Martin (69) and Nick King (67 not out) putting on 117 for the first wicket. John Franks took 4-41.
Hill scored over 200 for the first time this season thanks to knocks from John Wright (66) and skipper Paul Edwards (54).
Arundel and Clymping finished third and fourth respectively after the visitors won their West Sussex derby at Waterwoods Plain.
Arundel batted first and were all out for 156 after Adam Tester took 5-55. In reply, Clymping made 157-3 courtesy of an unbeaten partnership of 150 for the fourth wicket between Benn Challen (77) and Graham Blann (72).
Challen said: "It was a derby and in the past they have been quite heated. Last season's game was unpleasant and their captain and I decided to try and play the matches this season in a more sporting fashion.
"We are all looking forward to next season. We won seven of our last eight games and there's no reason why we can't be right up there next season."
Arundel veteran Neil Chitty said: "I think everyone is happy because we had a good season. We haven't had a settled side because of injuries and unavailabilities and we still finished one place higher than last term."
Bottom club Eastergate slumped to their 11th defeat of the campaign when they were convincingly beaten at home by champions Findon.
The home side batted first and were all out for 112, James Iago took 5-38. In reply, Findon made 113-3 with Graham Waller hitting 58 to complete their record-breaking seventh championship in style.
Pagham confirmed their best ever finish by finishing as runners-up after a 48-run win at Lindfield.
Pagham batted first and made 200-4 as Phil Harris hit 70. The home side were all out for 152.
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