Good in depth article by BCG's Chris Hallam on here on The Office's 20th anniversary this month. I don't remember it being an off season shown sitcom but I do remember it being on very late for a sitcom back then, about 10pm I think. In other words, the good old Beeb didn't have a lot of hope for it.
As he says, viewers weren't too sure what they were watching at first, I remember that exact feeling, I knew it was being funny but it was so different to what I usually watched that a lot of the gags went by me until about the third episode, the Quiz Night one, where I remember pissing myself laughing at this new sitcom monster David Brent, trying to cheat then getting the answers wrong. It's been my favourite ep ever since, although I'm well over due a full re-watch as I've barely seen it since.
Don't like the substandard cycle of copyist sitcoms STILL following in its wake, but that's also a measure of how great this sitcom was. clap clap.