Gooday MJI.....feel your pain. Humiliated at MOT station when they failed mine. Never seen so much yellow chalk under my car. What I could see was bad....but the inside rails which is hidden by fuel tank was scary. Can recommend RAC chassis at Birdingbury. They replaced my half chassis for £1500 which was about par for the course....lot of money but the quality of work really good. Not associated with them in any way......just saying. Hope you get it sorted.
Just checked my bill....was 1/3 chassis.....