The 21-year-old goalkeeper made a shock move to the Red Devils last year, and was included in their Premier League squad as an Under-21 player following his release from the U’s.
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Plumley, who didn’t make a first team appearance for either club, has now joined up with Hampshire side Hartley Wintney in the Isthmian League South Central Division, the eighth tier of English football.
Plumley made his debut for his new club, as they won 2-1 at home against East Grinstead Town in the FA Trophy first qualifying round.
While with the U’s, Plumley had loan spells with neighbours Oxford City, plus Beaconsfield Town and Weston-super-Mare AFC.