ISO 8859 codesets, and is poorly defined w.r.t. The first issue that surfaces is that the various ISO 8859 codesets don't have any consistent grouping of alphabetic vs. non-alphabetic symbols in the upper half of the codeset. As a result, each different ISO 8859 codeset has a different case-folding mapping. Even if you can solve the issue of identifying the codeset in question, the problem isn't completely solved.
Different cultures have different ideas about alphabetization of accented letters.