Lived in London during and slightly after university: it's not. City's pretty much dominated by cars, there's technically a transit system but it was slow and infrequent, and the way the city is laid out with three major N/S and three major E/W roads makes it hard to get around during constructions season. Downtown is...kind of walkable, but it's bordering on a food desert with only one (expensive) grocery store at the edge of the core.