For those that don't know, the reverse V for victory gesture (with your palm facing inward), effectively means "F U" in the UK.
It's a gesture that goes back to fighting the French - who cut those fingers off our captured archer's hands so they were no longer able to fire their longbows. So the remaining archers took to giving that gesture to show they still had their fingers and were about to use them to give the French some nasty splinters.
If you're still not sure how that gesture would look, take a look at the OLD image attached.
It seems Valve have picked up on this, and now our zombies are thinking they're Winston sodding Churchill. I don't know why, but this made me laugh. Valve have had to change that cover so many times it looks like someone just bunged their hand under the scanner, photoshopped it and said "there, bloody done with it".
Is it just me or is L4D2 just becoming farcical now?

was it ever anything more than that?

"I am not a crook."

I knew this story about the reversed V in UK, and still wonder if many americans (or even the Fox) knew it when watching Buffy. This was in the opening for many seasons.

Actually, that particular hand signal has been around for a long time. Seems noone knows where it first originated (except that it seems to be of British origin).
More info here, although I got my info from QI via Stephen Fry.

Dammit, you beat me to it. I was just about to reference that episode too :). If I could be bothered I would upload a siren .wav file so that Navagon could play it and feel shame :).

Not as far as I'm concerned, no.
I have heard quite a few different stories on its origins. There is some suggestion that it did occur, but it was only a one off incident involving a small number of archers, rather than standard practice. Does it actually have its origins in that incident? I don't know. I just like the story.

Oh Joss Whedon and James Marsters knew all about it. Spike threw it around a few times in the course of the series run and once on Angel. They never thought to mention it to the Fox guys. Whedon mentioned it on one of the DVD extras.

1st time I read that.
The Romans used to chop off Celtic archers fingers for the reasons you stated. Why do you bother with fingers ? We, French, would have just chopped their head off.

Well that's the story my Father always told me, but then, he hates the French so I'm not surprised he'd say that one. That and we were both avid archers back in the day =)
Still, the "new" cover is no better. It's either a farcical take at Sir Winston Churchill or there are some really scary zombified Japanese high school girls in the game.
Why do you bother with fingers ?
As far as warfare goes, it can usually be better to maim your opponent instead of just out right killing them, as it's a greater burden on your enemy.

Both shows were kind of weird when it came to British slang; in an early Angel episode Wesley jokingly calls Angel a 'wanker.' There's no way the character would do that (at least not at that stage); it's far too strong an insult. But Americans seem to find all British slang quaint and adorable, so I guess that made it perfect Wesley dialogue

Hehe well what about Futurama? Bender is a notably different word in england...

What's worse is that we refer to cigarettes as fags.
I need to nip off and suck a fag now.

Ahhh, different meanings of words. I remember concerning visiting English relatives by making them wait while "I find my other thong".

Ah yes, reminds me of hearing the term "fanny bag" a lot and not being able to stop laughing as a kid =)