If you stripped the screws holding the battery in like I did: I carefully tapped a small flathead screwdriver into the plastic casing of the battery surrounding the screw enough to break it. Then repeated this again so the plastic surround came away in three pieces. As this battery is going to be replaced with a new one, it didn't matter that I break it. Then with the extra room around the screw, used a pair of small sharp nosed pliers to get a better grip on the outside of the screw head and carefully unscrewed it. After replacing the battery, only one of the 3 screws was good enough to be reused, so put that back in the centre hole for temporary fix, and now shopping for new screw set.