rear exhaust mount on a clio mk2 phase 1

[cowan]

ive got a clio mk2 phase one 1.2 petrol and the bushing at the rear exhaust mount has split and i got a new one to replace it with but i cant remove the back mount as one bolt wont come off its mounted to the chassis leg and theres a nut on the other side but you cant get at the nut theres only a tiny hole which you can fit your wee finger through to see that the nut is turning. has anyone has this problem before as i have no idea how im going to get this one off and even tighten the other new one