[s-cars] Rear brake help please

[iain.atkinson at tesco.net]

Guys need some help please

my S6 failed it's mot (annual test in the uk) on the efficiency of the handbrake only 14%, now i know the cables are adjusted right up because i have tried once before to adjust them and can't get a socket on it (the adjuster rod is now too long even for a deep socket) so what to do, is it new cables or is it more likely the rear calipers giving up???? 

iain