United took the lead through Charlie Watt, but they were undone with the last kick of the game as the home side bit back to take the points.
"We played well," youth boss Eric Kinder said. "We took the lead and we looked good for it, but they got back into when we had a bit of a mix-up which they capitalised on.
"They went on to score in the 93rd minute, and that was really disappointing."
More details to follow.