had this problem with the locking nuts on my cq when my key broke - tried local garage etc and 12 point socket to no avail and then found that halfords do a 2 piece socket set for about £15 that worked a treat. These sockets cut into the locking nut - had all four done in about an hour ,bearing in mind that you will have to unwind the socket from the locking nut in a vice after removal and that the nut will be no longer useable.
Only tried it as a last attempt but was well impressed with this tool.
here's a link to halfords set
http://www.halfords.com/webapp/wcs/s...egoryId_165469