The BBFC Rating for U is for everyone can watch it and there is nothing
violent or any content that not suitable for children, where as U is
and any age can watch it.
PG rating is a parental guidance where children under cannot access the
film the only way they can is by parents being there and parents
can decide if they want their child to wathc it.
12A is for 12 years and up as this would include some minor swearing and if your under age you have to be with an over 18.
15- you have to 15 or over to watch the content as it has very strong
lanuage, violence so it would not be suitable for under 15 as it would
not suitable.
18- This is only for adults as it has full nudity scenes and full on swearing, violence as it has lot of detail on it.