For me the monetary distinction in classes is simple.

Working class equals, working to survive, living day to day with little opportunity to progress as you get by, hand to mouth.

Middle class are independently self sufficient with the ability to save and purchase everything they need or fund debt to provide it.

Upper class generally have more wealth than they know how to spend and provided they don’t have a member of the family that just blows it all then they will continue to become more wealthy.

There will be some who fall above, below and between those classes. I’ve got absolutely no idea how this compares to an official description of class distinction, however at one time it was easy to know where your vote was going to be placed based on which class you generally fell under.

As most have already said, this is no longer the case. The left have lost a lot of support amongst the working class but possibly gained small numbers amongst the middle classes. If they are to ever achieve anything in politics again they need to address their core supporters concerns.