No, the drinking age should not be lowered in Britain, because alcohol affects the brain of a young person differently. Someone who starts drinking at a young age is more likely to become a substance abuser later on in life. Young people act more dangerously when they are drunk than when they are old. There is plenty of time to drink later on in life.
In the UK the legal drinking age is already quite low compared to the rest of the world, it is at 16 I believe, and that is plenty low enough. Any lower than that and you are almost forcing liquor on to children. At that young of an age if these kids want to drink they have to go through a parent, which is more responsible and will keep more problems off of the street.