Not sure anything's eluding you. Class is a tricky one as it's certainly fluid for a person through their lifetime, or can be. My take on that is that for political discussion, it's important not to think of, say, Alan Sugar as working class. That he has a working class background would be a better way to describe him, which is frankly irrelevant when considering his role and that of the class to which he now belongs in the workings of economies. Going the other way around, I used to have a neighbour, fifty-something, skint, with drink problem and some MH issues, just about getting by in a council flat, who spoke kind of posh and went to a private school. He had a middle-class or upper-middle-class background, but that certainly wasn't his status by the time I knew him.
Defining class is another huge can of worms. God help me I more or less agree with phildwyer on this one in that today, many people have a mixed relationship with the means of production, being to some extent both workers and bourgeois with potential for income from owning stuff. Easiest and clearest way to work out your economic class is to have a look at your bank account and see how much comes in every month, plus add-ons like stuff you own, stuff you might inherit, and social capital like education status or who you know.