I got an internsip at a City law firm last summer, and I met a guy there who was my age but kept going on about 'daddy's money.' He got the internship because of 'daddy's connections', he was going to live out in university on 'daddy's money', he was going to get a car (can't remember the name) with 'daddy's money'... I thought he was posh, mainly because he kept boasting non-stop about his so-called superior daddy and his so-called superior mummy and their so-called superior 'two-parent family who could get him places and brought him up well' etc. Basically, he thought he had to flash his money around and that this made him better than me. The funny thing is, I worked alongside hundreds of suited men and women who were rich- I met sooo many public-school ecuated people. My supervisor used to ask me every night if he should order me a taxi home because he's never used public transport and he would never let his daughter use it if he could arrange something else. These people all spoke with an accent that I'd only heard on the Radio 4/Parilament channels etc. Yet I didn't consider any of them 'posh'. Just the guy I mentioned.
Also funnily enough, now that I've done well education-wise, started working, got a conditional offer to study Law at a good uni, and basically embraced academia and education, I'm branded as 'posh' by people I've known from way back. My accent hasn't change, I still speak the same (though my English when typed has dramatically improved after having to type out thousands of official letters), I still live in a council estate. I still have to deal with the same crap I've always had to deal with, but because I'm not wondering the streets like I used to, I'm suddenly posh.
All this has left me very confused and sceptical about the concept of 'posh', I don't believe that many people are. The question of who was posh was so much easier for me back in the day, I used to think everyone with a little extra money, everyone who could afford holidays and everyone who spoke standard English, etc was posh. Now, I don't think that's true, but I also don't know how to define posh...