The Three Lions, managed by Paul Fairclough, took the lead in the first half when Hyde forward Scott Spencer scored from the penalty spot but the Belgians levelled when Arne Naudts equalised.
Town midfielder Adam Watkins came on in the first half, and was joined by Gray after the interval, as he scored the winner 11 minutes from time.
Club-mate Greg Taylor became the third Luton man to join the action late on as England held on to secure victory in their attempts to qualify for the International Challenge Trophy.
After the game, Gray tweeted: “Buzzzzinnnnnnnnnnnn.. Scored the winner for England.. Thanks every1.”
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