This is what the MOT Testers Manual says about Corrosion.
To assist with the assessment of corrosion sections 2, 3 and 5 of the manual identify the parts of the vehicle structure which are particularly important and to which particular attention must be paid during the inspection.
These are:
- The load bearing parts of the vehicle to which certain testable items (as specified in section 2, 3 and 5) are mounted.
- Any structure or panelling which is supportive to either the component mounting or its load bearing member within 30cm of the mounting location. eg. In the examination of a seat belt mounting on an inner sill, consideration must be given to the outer sill, door pillar, floor panel, wheel arch or any other supportive structure within 30cm of the component mounting point.
There's no way the inner wing on a disco can be described as been supportative of the bulkhead or any of the components on the bulkhead. Therefore it's not testable. And n MOT tester can only go on what the manual tells him. He is not allow to deviate from it at all.
Here's the website for anyone who wants to read up on the MOT before taking their landy in for it's test. The full manual is on there.