For the mot, is no corrosion 30cm from mounting pointsort of - wot i mean is the inner wings aint part of the MOT, EXCEPT that a hole thro them colser than 8"? to the brake servo IS a fail - and that includes the rear part of the iner wings.
YRM do replacements and i think there is a "how to" in General Q's section.
30cm - thas aboot a foot in old money -