If they cut out most, if not all the swearing, I believe it would have been at least a strong PG-13 movie, due in part to the talk of sex, but mostly by some of the tense situations at Billy's house and the violence. About the only movie I've ever seen that has a strike in it and was PG was the Disney musical Newsies, and they cut out most of the violence (and all the blood). Any violence that was left was more staged, complete with comebacks and such.
I think the cursing allows more people to get drawn into the life of the miners in the 1980's (remember, not all people react the same way to movies) and gives it a bit more realism. Thankfully, since the West-End/Broadway shows are out, more people are buying/renting Billy Elliot, so many people are still watching it.
Rich,
I guess there may be more swearing publicly if the shock value is less. With that being said, some of the filthiest mouths I've encountered on this side of the pond have been Boy Scouts on camping trips (or worse, at summer camp). Talk about shock value, at least to the average citizen. If you were ever a scout (when you were at least 12 or 13), you'd understand.
I will not take the name of the Lord in vain, but I personally am not offended by cursing. I do understand that there are people who are and I respect that. I try not to curse in public or around my parents out of respect. If you are that offended by cursing you are really limited in the movies you can watch. I wonder who and when in society that these select words were determined to be "NAUGHTY" 
I started rambling sorry, I just wanted to say curse words are not offensive to me, but respect that people should not be subjected to it if they care not to hear it. 
