thats not the rust, it will be just behind the sill lip i would guess.
and dont buy cv gaitor repair kit, get a proper one fitted, do it your self if you have the tools, its 2 bolts basicly, only special tool needed would be a ball joint splitter but seeing as its offroad atm, you can try and do it without first, and if all else fails get it done at a garage but you shouldnt have a problem.
:yeahthat:
The 'rust' in the pictures is merely surface rust on the rear beam axle. This is not what was meant by the MOT report. The sill has outer and inner sections with the outer being visible as the ledge that runs from the bottom of the doors(and between the front and rear wheels) to the underside of the car. The inner sill runs from inside the car as well as sections underneath the floor where it joins with the outer sill.
I suspect that the sill that's corroded is at the back end in front of the rear passenger wheel. Stand by the passenger rear wheel and put your hand underneath the sill and feel behind it. This is a common place for the sill to begin rusting so you may find chunks of rust coming away or even a hole. If possible, look behind it too as that will confirm for sure if it's this area that's caused the fail. A mirror may help or simply take a picture holding the camera facing that way underneath the car.
Let the forum know what you find