On a glorious day at Fulking, Ben Twine won the toss and elected to bat. Alastair Orr (33), Scott Lenham (54) and Oli Carter (47) helped them reach 207-6 from their 40 overs.
In reply, East Grinstead found themselves in trouble at 82-6, but Brad Hatchett (41) and skipper Darryl Rebbetts (26) led a mini recovery before Toby Pettman (52 not out) took Grinstead close.
But Scott Lenham halted the late charge with 3-36, including Sam Rattle in the final over which secured victory.
In the Group A5-A8 final, Slinfold chased down the the 180 target set by Crowhurst Park in an astonishing 14 overs. Tom Endacott and Guy Thorne took three wickets apiece before Adam Goacher (60 from 30 balls) and James Parker (62 from 25 balls) helped make short work of the chase.