I'm english but not very good with accents.
McGonagall is Scottish.
Hagrid's accent i would say is Devon/Somerset/Brsitol. (yet Robbie Coltrane is actually Scottish i think)
Both Weasley Boys (George&Fred) have Birmingham accents.
Seamus is obviously Irish.
Gambon as Dumbledore has a slight hint of Irish in his accent
Luna is Irish
Harry just sounds normal to me,
I would say Hermione sounds like she's from Oxford (quite posh)
Ron also has a normal accent.
(in my opinion
)