To be more clear about where the chimney I'm talking about is - it's about 2-4m directly below the second belay point. From the topo in the guide book (p232) it looks like there are three cracks/gaps that go up to the belay - the offwidth chimney is (obviously) the larger of the three - and the route line goes up the far right crack. These other two cracks are sort of around a bit of a curve, although that's not obvious from the photo. When you're actually at the bottom of this chimney you can't see the other cracks and it's really exposed, which is probably why I decided to go up rather than to investigate further.