I found a rare cool resource in the form of a comment from the old place about the various accents of the characters of Harry Potter, in the films. This is not my post or comment. Credit to Travy911
Harry (Daniel Radcliffe): Contemporary RP accent
Ron (Rupert Grint): Speaks with more of a Cockney accent in the earlier movies but transitions into a less posh sounding contemporary RP accent than Radcliffe and Watson. Grint has commented himself on how surprised he is by how Cockney he sounds in the earlier films.
Hermione (Emma Watson): Contemporary to classic RP. Watson sounds the most posh out of the trio.
Most of the cast speak with contemporary or classic RP. Many of the older actors especially would use classic RP as that would have been the go-to accent in the earlier days of British film industry. The following exceptions are below however.
From the remaining Weasleys, Ginny (Bonnie Wright) has a contemporary RP accent. Percy (Chris Rankin) has what approaches classic RP which would reflect the character's social climbing ambitions. Mark Williams, Julie Walters, James Phelps, Oliver Phelps (Arthur, Molly, Fred and George) are all from the West Midlands which has its own distinct accent(s). This can be heard very faintly in their accents with Williams probably having the strongest accent. But Brummie (Birmingham accent, Birmingham the biggest city in the West Midlands) and Black Country accents (the surrounding area) can be much stronger. Domhnall Gleeson (Bill) is Irish but adopts a sort of Cockney-ish accent in the few lines he has as Bill.
Seamus (Devon Murray) and Luna (Evanna Lynch) have Irish accents. Murray and Lynch both grew up close to Dublin but Murray's accent is closer to a working class Dublin accent. Lynch's accent is more faint, neutral sounding and difficult to place in an exact region, heard in a lot of young Irish people. Rhys Ifans (Xenophilius) is Welsh but adopts a similarly neutral Irish accent. Xenophilius and Luna's nationality is never confirmed in the books.
Brendan Gleeson (Moody) is Irish and uses his natural Dublin accent in the role. Moody's nationality is never given in the books so not sure where you got Scottish from.
Richard Harris (Dumbledore in the first two movies) uses his natural Irish accent. Harris was a classically trained actor and spent much of his adulthood in Britain so it is mostly a soft Irish accent with the tiniest English lilt. Michael Gambon (Dumbledore in the later films) has a more pronounced English accent but has an Irish lilt to certain words to honour Harris' portrayal. Gambon was born in Ireland but primarily raised in England.
Katie Leung (Cho) and Sean Biggerstaff (Oliver Wood) are both from Glasgow and have typical Glaswegian accents. Katie Leung's accent is less strong and she acknowleded her Glasgow accent is stronger when around family on James and Oliver Phelps' podcast. Cho and Oliver's nationalities are never confirmed in the books.
Maggie Smith (McGonagall) is English but adopts a Scottish accent for the role, more like an Edinburgh accent. McGonagall was always implied to be Scottish in the books and Rowling confirmed she was from Caithness which is in rural northern Scotland. The Edinburgh accent is considered the "posh" accent in Scotland so makes sense that McGonagall might speak with this accent so she's more understood by students.
Robbie Coltrane (Hagrid) is Scottish but adopts a West Country accent for role of Hagrid, which makes sense as Rowling writes his dialogue in a West Country accent.
Matthew Lewis (Neville) maintains his strong Northern Yorkshire accent in the role.
Shefali Chowdhury (Parvati) is from Birmingham and has the accent. Afshan Azad (Padma) who is from Manchester and has a Manchester accent confirmed in a YouTube video that she was asked to adopt Chowdhury's Birmingham accent for Padma as she states she's quite good at accents.
David Tennant is Scottish but like many of his famous roles has adopted a contemporary RP English accent as Barty Crouch Jr. Fiona Shaw (Petunia) is Irish but mostly has a classic RP accent as Petunia. Her Irish accent is more pronounced in the deleted Deathly Hallows scene where she acknowledges death of her sister. Shirley Henderson (Myrtle) and Kelly Macdonald (Helena Ravenclaw) are also Scottish but adopt RP English accents for their roles. Ian Hart (Quirrel) has a Liverpool accent but sounds more RP in the movie.
The international cast featured in Goblet of Fire are all cast appropriately based on their nationalities in the book and have the natural accents that go with it. Clémence de Poesy (Fleur) is French and Stanislav Ivaneski (Viktor Krum) is Bulgarian like their characters. Frances de la Tour (Madame Maxime) is English but with French ancestry and seems to adopt a decent French accent. Predrag Bjelac (Karkarofff) is Czech-Serbian. Karkaroff's nationality is never confirmed in the books but his name is Slavic in origin, which is the language group both Czech and Serbian belong too (although Slavic is large language family so someone with more knowledge could probably talk more about this).
Lee Ingleby (Stan Shunpike) has a strong Cockney accent in role, as Rowling wrote Stan's dialogue in this accent. Nick Moran (Scabior) also has a Cockney accent as Scabior.
Hopefully that covers all the accents! 😁
end