In an attempt to further multiculturalism on the forum (or more realistically to poke fun at the english mother land) I've got a burning question on proper grammatical structure.
I've noticed while watching a number of British television shows (See Top Gear, Doctor Who, The Office, etc.) that english speakers from over the pond (over the pond in the easterly direction that is) frequently use the phrase "It's a good job that_________" to mean "It's fortunate that________". Meanwhile, American English uses "It's a good thing that_________" to say the same thing.
For example, if someone got in a car accident you might hear
British: "It's a good job that I put on my seat belt"
American: "It's a good thing I put on my seat belt"
or, if you fell off a building someone might say
British: "It's a good job that this truck full of pillows was here"
American: "It's a good thing this truck full of pillows was here"
So my question is this: Is this a case in which a colloquial phrase is seen as acceptable when in reality there is a proper rule which says "It's a good job" is not allowed or is this phrase considered the proper way of saying "It's fortunate"?
If it's the later, I'm intrigued because to my ears it sounds as if they would be giving themselves credit for an instance of luck and happenstance.