'Strong violence' is permissible in '15' certificate films:
http://www.bbfc.co.uk/what-classification/15
(Click the links on the left to compare with other certificates)
Attitudes to on-screen violence seem to vary greatly across the world. The USA is less restrictive than the UK but Australia is far more so. (For example, when I was in Oz many years ago, I saw 'The A-team' on telly there. In the UK it was being shown in the peak family-viewing slot on early Saturday evenings. In Oz it was on late at night, with an '18' certificate shown on the screen beforehand).