[mytailorisrich]

> just that if you lived in a member country for 5 years you automatically get the right to permanent residence there

No, you need to meet additional criteria. This is explicit in EU law [1] (and very well covered online), so I'm puzzled as to the advice you received.

Since you were looking for a legal references regarding students, note that [1] is also explicit that students should have "comprehensive sickness insurance cover" (the dispute here is whether access to NHS qualifies. UK government argues that it does not).

[1] Article 7 of https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX%3A...