Alien age restrictions in England

The only time I worried about Alien's audience was when I was in England, after the Worldcon. I went to Birmingham to do a presentation. After my presentation, I talked to a group young boys -- I think they were 11 to 13. England has very strict rating system which separates movie goers by age group. They have a category called Nasties. It's a different rating system than the one we have in the us. I worried we'd be limited in our UK market because their system allows for the arrest of selling video Nasties or box office Nasty tickets to underage kids. This group of young boys assured me there was no way they would be kept from seeing the film. They said if it got a Nasty rating, they'd still be able to see it.