I've found the BBFC insight really helpful
www.bbfc.co.uk/what-classification/what-bbfc-insight
It doesn't have it for the older Harry Potters but gave the following for deathly hallows
HARRY POTTER AND THE DEATHLY HALLOWS - PART 2 is the final film in the series about the young wizard and his friends, Ron and Hermione. The three friends return to Hogwarts where they prepare for a final showdown against Voldemort. The film was classified '12' for moderate threat, injury detail and language.
Like HARRY POTTER AND THE DEATHLY HALLOWS - PART 1, the film is quite dark and there is a sense of threat throughout. A number of familiar characters are shown in danger, and some of them are injured or even killed in the various battles that take place. However, the sense of threat is moderate rather than strong and 'disturbing sequences are not frequent or sustained,' in keeping with the requirements of the BBFC's Guidelines at '12A'/'12'. There are some sad moments, particularly when familiar characters are killed, but these scenes are handled sensitively. It is also likely that many viewers will already be familiar with the story from the books, reducing the impact of these events.
The violence is generally quite undetailed. There are large-scale battle scenes in which blood is visible on the clothes of the injured and dead afterwards, but without clear injury detail. A stronger sequence occurs when Voldemort orders the murder of a key character, leading to them being repeatedly bitten by a snake. We hear the attack rather than seeing it, but there is quite a lot of blood on the victim's neck and on the wall behind him afterwards. The Guidelines at '12A'/'12' permit 'occasional gory moments' and there is no close-up injury detail or clear sight of injuries being inflicted. Another gory moment occurs when Harry enters a dreamlike world and sees a bloody foetus-like creature, which is clearly not human. It is only shown briefly and Dumbledore speaks to Harry about it, reassuring him and reducing any potentially distressing effect on younger viewers.
The film also includes a single and aggressively directed use of the word 'bitch', during a fight scene. The Guidelines at '12A'/'12' state 'Moderate language is allowed'. There are also several uses of milder language, such as 'bloody' and 'bloody hell'.
Parents can find additional information about the content of this film if they visit www.pbbfc.co.uk.
I think - reading this you, as a parent, can make the call.
We went through all the Harry Potter films quite slowly, DD6 and DD4 are not allowed to watch the 12 rated ones without us watching it with them. Also eldest daughter wanted to know more detail on the plot which the film glides over - so i've told her she has to read the book if she wants the whole story.
They also play being witches and we're going to Harry Potter world 