Our 2nd car is a low mileage '98 1.3 LXi.

The n/s rear susp unit has just broken, the spring seat on the s/a has rusted thru!

Easily fixed with a new susp unit but is this a common fault?

Very common, also happens on the front struts.

happened to the rear one on my favorit, Same strut, so i assume same problem.

like you said, easily fixable.

i think the key is to make sure that the drainage holes in them do not become blocked.

other than that i think its just the original ones dnt last very long. but the replacements do.