Many novelists don't bother with chapter titles. Nobody else seems to have noticed - though I suspect a teenage reader will get it. That was the idea. Also, I enjoy it. I enjoy the wordplay as a writer, and as a reader I find it much more interesting to have intriguing 'signposts' along the way.
Writers using numbers as chapter headings is a weird concept.
I've heard you talk with biting irony about going into an Our Price shop on one side of the street, seeing it teeming with teenagers spending pounds and pounds on CDs, then walking across the road to a branch of Waterstones, finding the Young Adult section tucked away in a corner opposite books on breast-feeding, copies of Soundtrack on the shelf, but not a teenager in sight. Gardening gets more space and presence than Young Adult fiction. There are loads of things that could be done, now. It's just not cool. I've just heard Anne Fine rant most entertainingly on book covers, among other things, at the Edinburgh International Bookfest.