Heath won the Southern Combination Football League at the second time of asking last season, and the Mid-Sussex side started brightly as Karl Akehurst and Melford Simpson both went close early on.
At the other end, Jack Spong fired over after neat build up play, before Heath were handed - quite literally - the chance to break the deadlock on 21 minutes. Tariq Shahib was adjudged to have handled from Simpson’s flicked header, and Saunders slotted the resultant spot-kick down the middle and beyond the despairing Billy Collings.
Simpson, a menace throughout with his power and physicality, had another header saved and Finney had an effort blocked by Shahib as Heath turned the screw in search of a potentially decisive second.
Ashman flashed a shot wide from distance but still it was Heath who continued to carve out the better chances. Collings was called into action again to keep out the livewire Simpson, and Akehurst went close again from distance.
A tie in which chances were at a premium appeared to be drifting to a benign conclusion but, rather like the stormy weather that suddenly engulfed the County HQ, the contest sparked into life.
Brighton had rarely looked a threat but, as the clock ticked into injury time, they went within inches of a leveller twice in quick succession.
First, substitute Sam Packham headed agonisingly wide having been picked out by Jayden Onen, before another header seconds later - this time from Stefan Ljubicic - dropped a fraction past the post with Josh Heyburn scrambling.
An equaliser would have forced penalties and it almost came with the final action, as Heyburn came to his side’s rescue in the fifth additional minute. He saved superbly from a Ljubicic free-kick, the resultant flag kick fell to the same player but he was unable to provide a dramatic ending to this season’s opening curtain raiser.