Derusting & painting underneath of van advice

[Spiral]

Was thinking of wire brushing/treating/painting various spots of minor surface rust underneath my westy atlantic before it gets any worse. What I want to know is should I leave certain parts of the underneath of the chassis untouched? Don't really want to fall foul of MOT tester who I'm concerned might view this with some degree of suspicion Thanks in advance

[kevtherev]

you won't fall foul... bollock it on