Working class and upper class children seem to have this freedom in London, having lived in both to press of area.

When I lived in Richmond there were often children alone on the bus or train with expensive belongings like musical instruments or sports equipment. My middle class parents would never have allowed that - but they would expect me to get to school on public transport alone.

Also, there are no rules or laws against this. It's cultural. See http://www.btp.police.uk/advice_and_information/travelling_s... for one example - there's no minimum age to travel alone on a train.