I did suggest Googling for 'screw extractor' as there are numberous types on the market. Here is one that doesn't require any drilling into the screw.
http://www.machinemart.co.uk/shop/p...ve/path/05-drill-bits-screwdriver-bits-steels
http://www.machinemart.co.uk/shop/p...ve/path/05-drill-bits-screwdriver-bits-steels