This first round qualifying replay followed on from a 1-1 draw at Hanbury Park on Saturday last, when the Blues came from a goal behind but that luxury was beyond them, this evening.
The Hornets scored after 38 minutes when Billy Collings, the Blues keeper, put through his own net, and a second goal followed from the penalty spot, courtesy of Charlie Harris, on 73 minutes to seal Horsham' s place in the next round of this year's competition.
Neither side bared their teeth in a cagey opening 15 minutes, however Horsham began to take control of the midfield area and the visitors had to defend well.
The Blues were unlucky when Jordan Clark played Sam Remfry in, but Saturday's goal hero, flashed his shot the wrong side of Sam Howes' right hand post, whilst many in the crowd were holding their breath, expecting the net to bulge.
With Horsham now dominating proceedings, a raid down Heath's left side on 31 minutes, saw Lee Harding play Shamir Fenelon in and only a great diving save from Collings prevented the home side taking the lead.
Heath's Tom Summerfield was given a yellow after a poor challenge, where some home fans felt it close to a penalty.
Parity was broken a few minutes later, as the busy, Lee Harding, delivered yet another corner into the Heath six-yard box. The flight of the ball may have been lost by the Heath stopper because it struck him and rolled over the line to open the host's account, in the strangest fashion.
Haywards Heath were unable to get much of the ball as wave upon wave of Horsham attacks came flying towards their goal.
Collings, the Heath keeper, showed strong resolve in keeping Horsham out as they finished the half showing their best. Given some last-ditch clearances and maybe the Hornets' lack of sharp finishing, the score remained 1-0.
The second half continued with the hosts in determined mood to seal the tie and, on 54 minutes, Tom Richards ghosted past Hamish Morrison, sending in a great cross to the far post, where Harding rose above all challenges to head back across the goal, leaving Collings clutching at thin air and the home support cheering the ball across the line but there was Sinn Christie, making a timely clearance to keep the ball out.
Heath were again being forced back in midfield and they couldn't find any way through the resolute back five of Horsham.
In a two-minute spell the game was turned massively in Horsham's favour with the substitution of Fenelon, who was replaced by Rob O'Toole.
Almost immediately, O'Toole played Jack Brivio into the Heath box where he was brought down by Christie, giving referee Steven Scott, no option but to award a spot kick.
This was duly driven down the middle of the goal by Harris, and under despairing Collings, to send Horsham through to the next qualifying round.
Despite making changes and sending big Nathan Cooper up front, Heath weren't able to find any progress and Horsham's nous and game management comfortably saw them win in front of a gate of 441.