Oh dear Chris, sorry to hear it but its virtually impossible to kill off the rust without cutting it out. The 126 is made from notoriously bad steel, its of Soviet origin and is recycled steel. When steel is recycled the carbon content is reduced during the proccess, a decent recycler of steel can overcome this but those Ruskis didnt! What this means for us is that the steel the 126 is made from rusts badly as soon as its exposed to air and moisture. Its fine whilst protected but obviously Fiat didnt protect it that well, thin paint, minimal rustproofing. I remember years ago having various old English cars covered in stonechips and they never rusted until the salt got to it, but our old Fiats start to go as soon as the metal is exposed and once its in there its hard to stop it!