I have had an '01 TD5 90 for 4 Years - but I have done low-mileage due to the Jersey factor. So far no mechanical issues whatsoever (including the Air-con) Check the chassis thoroughly, and watch the bodywork. The ali panels can get electrolysis issues that are as unsightly difficult and expensive to fix as good old fashioned rust.
The 90's have surprisingly little storage space, and extensive test drives are a must, they do not drive or ride like cars, they are trucks.
But beware they are (almost) as frustrating, addictive and sheer fun as Mogs