After a goalless first half, Seymour was called upon to superbly deny the Blues’ Sam Cornish, Dylan Kearney and Alkeo Bani.
Wingate were given a golden opportunity to extend their three-match unbeaten run when they were awarded a penalty with a minute of normal time remaining.
But Horsham stopper Seymour did brilliantly to keep out Wilfred Ompreon’s spot kick, and less than a minute later substitute Shamir Fenelon fired home to give the Hornets a late lead.
Tom Richards doubled Horsham’s advantage in stoppage time from the penalty spot to move the Hornets up to tenth in the table.
See some pictures by the club's photographer John Lines on this page and the ones linked.
Get the latest from the Camping World Community Stadium in the West Sussex County Times - out every Thursday.