I think I paid around a fiver for a Snap-On socket. Use a half-metre breaker bar and job done. Mind you, be careful this doesn't happen. Once I'd got the normal overtightend bolts out I moved on to the BMW locking bolts. And then this happened:
Mickey-Mouse metal and over-tighted with an impact gun.
Right pain in the arse that would be on the hard shoulder of the M6.
Current: 2013 F10 520d M-Sport, Professional Media, Visibility Pack, Reversing Camera, DAB
Previous: 2011 F10 520d M-Sport, 2008 320i M-Sport Coupe, 2002 325i, 2001 318i valvetronic, 1998 318i, 1996 525i, 1990 Porsche 944S2