In this particular episode, the hero Dave Lister seemed to have contracted some form of “mad” virus that affected him with psychosis, creating two personas in the process (Confidence & Paranoia).

I have never seen the show, so plot spoilers aren’t due. However, there’s this one scene in the said episode where “Confidence” took off his helmet during a spacewalk to prove (presumably to Paranoia, but this is just my guess) that “Oxygen’s for losers.”

If my guess is correct, this should be the origin of the “phrase,” if one can call it that. As for its meaning in the current vernacular, I can only guess. You can try posting this again in the Y!A UK & Ireland section. You might be able to get a more accurate answer there. Anyway, here are some of my guesses as to its usage(s?) in the current vernacular :

1.) a foolish attempt to show off even at the risk of one’s life.

2.) an emergency attempt to rescue a person from a near brush with death after showing off at the expense of his life.

3.) a snide remark for people who need to be pushed in order to get ahead.