The Wolves now go into the weekend's Challenge Cup semi-final against Huddersfield in winning form after dashing the Dragons' hopes of usurping them from second place.
Westwood opened the scoring on his return to action after a hernia operation with 13 minutes gone. Brett Hodgson added the conversion.
Ryan Atkins added a second try for the hosts on 51 minutes but the Catalans struck back seven minutes later as Jason Baitieri touched down.
Scott Dureau's kick cut the gap to four points but a penalty by Gareth O'Brien soon after put the Wolves back in the ascendency.
Michael Monaghan then kicked a drop goal to leave the visitors needing two scores to get back into the game and when Hodgson kicked another penalty with two minutes remaining, the points were sealed.