Use a Ezy Out, you can buy them at any tool store for a few bucks (Canadian tire has them) follow the instructions, basically you use your drill to get them to bite the stripped bolt, then reverese the drill and it unscrews them, real easy and so simple. edit - Oh see your from the UK, Halfords will probably stock them, or B&Q
last time i used super glue i found an old Allen key i didn't need. then put super glue in the rounded bolt and let the Allen key dry inside of it. it held on pretty well. but it might not work on a brake pad.
also make sure your using the right type of tool for it. sometimes on avids they will put torx and allen bolts on the same product which is just confusing.