I would agree. In the US any class is defined by the social safety net they have and in the current workforce it's often entirely self funded with many parents/older generation reaching into the pockets of their children for labour or money. Even people living a 'middle class lifestyle' are one bump or bruise away from losing everything. Since the UK has a different expectation of a social safety net I can see how things might go in a different direction. If I was not constantly under the risk of healthcare costs blowing up what little I have built up then I probably would consider myself middle class. But since my income stops as soon as I stop and I don't have a huge runway to get going again I don't feel like I'm in the middle at all.