The Styal professional started the tournament lying 71st in the European Ranking with the top 60 being invited to the World Championship in the Emirates in a month's time.
Horsey, who strung together five birdies in seven holes from the third, is tied sixth and four shots behind defending champion Sergio Garcia who endured the worst of the weather for his 63.
Macclesfield's Jamie Donaldson is on level par with Bromborough's Paul Waring one further back.
LANCASHIRE'S David Shacklady finished ninth after a brace of 71s, two-under-par all told, in the Srixon PGA Play-offs at Little Aston, five shots adrift of winner Michael Watson, from Wessex.
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