Osbaldwick became the first division three side to know their fate when, after being whipped out for 58, they suffered a nine-wicket defeat at Woodhouse Grange and cannot now escape from the bottom three.
Hornsea's star batsman, Mike Johnston, had one of his rare failures but then turned in a handy bowling performance to help his side to the better of a draw with Heslington. That leaves the league newcomers requiring only 29 points out of a possible 120 to ensure promotion.
Stand in opener Guy Martinson rose to the occasion for Hornsea hitting 91 in only his second innings of the season.
Skipper Dave Prescott got in on the act with 74 as Hornsea totalled to 251-6.
Heslington then made a good start with 100-1in 23 overs through Mark Fratson 36 and John Myers 32.
But Johnston then produced his best bowling figures of the season as he captured 5 for 35 to reduce Heslington to 147-6.
Malton and Old Malton's game at Cawood produced a similar result as with Malton's 221-5 being followed by Cawood moving to 117-8.
Malton's runs came mainly from Greg Johnson 80 and Neil Johnson 66, while Andrew Raines chipped in with 57.
Nigel Bartram was Cawood's best bowler with 3 for 60 but his figures were bettered by Danny Foxton who took 5-42 to restrict Cawood, for whom Stuart Baxter made 48, to 117-8.
Bolton Percy did their survival chances a power of good when they beat Selby despite having to bat first.
Colin Thacker made 61, Howard Hall 36 and Nick Lister 35 as Bolton made 179-3.
In reply, youngsters Matt Hoyle made 33 and Steve Spence 27 but Selby were unable to hold out and were dismissed for 132. Chris Beeley took 4 for 29 and Richard Douthwaite 3 for 29.
New Earswick's Paul Stimpson gained his second successive seven-wicket haul when he took 7 for 46 to dismiss Londes-brough Park for 125.
Park's Phil Curtis then took 3 for 53 but James Routledge made 41 and Andrew James 37 to help Earswick gain a narrow two-wicket win off the final ball to keep themselves in touch with the two leaders.
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