How can you remove oil plug from sump alan key rounded off on a vaux combo?

If the oil plug on your Vauxhall Combo has a rounded off alan key socket, you can try using a pair of vise grips or locking pliers to grip the edges of the plug and turn it counterclockwise. Alternatively, you can cut a slot into the top of the plug with a Dremel or similar tool and use a flathead screwdriver to unscrew it. If those methods fail, consider using a bolt extractor designed for rounded fasteners. Always ensure the engine is cool and the vehicle is secure before attempting to remove the plug.