One pound (100 pence) in British Sterling (GBP). Can refer to the actual denomination (a goldish looking coin, about a centimetre and a half across), or any amount in Sterling. In very common use, all across the UK.
"That'll be a quid mate"
"That's going to set you back about 3, 4 hundred quid"
Someone who hails from London. Not to be confused with a cockney; to be a cockney you have to come from East London. Believe it or not, there is also a West,North & South London.
"You from Essex mate? You sound like like it"
"Nah. I'm a Londoner. Move to Hertfordshire when I was 13 though"
Someone (esp. on an Internet 'forum') who is actively negative, and sees the bad in everything. This doesn't necessarily reflect their public persona, but rather takes advantage of the faceless nature of the Internet to rant and rave at strangers without recourse. Similar to a troll, but not as antagonistic, pissfaces can also be called miserablists, pessimists or Grumpy Old Men.
They are often characterised by taking jocular comments at face value, finding offence where none was intended, and purveying a general attitude of negativity.
The term comes from the (supposed) 'sour' qualities of urine.
"Actually, that portion of the film is regarded as one of the finest in modern cinema. Before you see fit to criticize it like that, you should ask yourself what you *really* know about cinema. You disgust me"
"Please, don't be such a pissface"