Henson joined the Kassam Stadium club last month and Jones believes that the 30-year-old is finally taking his career seriously.
"Gav has had three or four years of fannying around and not being serious about his rugby," he said.
"He has grown up and he realises now he has four or five years left in the game and he wants to give it his best shot. He is training hard and he's enjoying himself."
Henson's contract with previous club Cardiff Blues was terminated in April following an alcohol-fuelled incident on a flight from Glasgow to Cardiff.