POSH?

Weight: It's been a while since I've been to the gym so no clue
Units of alcohol: 1.5
Subways: 1/2
Awesome flatmates: 2

The main difference between Cardiff and Portsmouth Universities is that here I get called posh and I never was there.  Why is this?  And let's discuss this because it bugs me.  Dictionary.com defines posh as:

1.smart, elegant or fashionable
2.upper-class or genteel


However, people also use this to mean having lots of money and talking in a certain way.  I need to clear a few things up.
Yes, I can dress smartly but so can anyone if they make an effort.
I am anything but fashionable.  I buy clothes from the high-street and have been described as dressing like a granny.
I am so not upper-class.  I am most probably middle-class.  My grandmother could possibly be described as upper-class as she went to finishing school, did a cordon bleu cookery course and was one of the last débutantes to be presented to the Queen.  But that is her, not me.  Yes, she sent me to boarding school but only on a scholarship and I greatly appreciate the opportunities I have had which stem from that.
I don't have lots of money. I'm living a great student life because I get lots of means-tested free money from the government, but that's only because my mum earns peanuts/single parent family.
I don't buy Tesco Value food because most of it is utter shit.  I barely ever buy anything unless it is on offer. I like to buy Lurpak butter but what's wrong with that? I like it.
As for how I speak, I don't talk posh, I speak properly.

*Apparently my brother gets called posh too. His response is 'I'm not posh, I'm privileged.'*
http://www.youtube.com/watch?v=bn0hFnOGnq4