Okay it looks like arm-2008q1 is the last 4.2.x Glib - this is derived from where I would install the kernel headers
Updated the buildroot bug report to reflect this
https://bugs.busybox.net/show_bug.cgi?id=5486
2008q3 goes to 4.3.x which I assume is the break to 2_7... correct me if I'm wrong.
Would that be the info I have been looking for?
The final departure point of CS away from 2.6
Going to skip down to 2008q1 and build up from there. see what shakes.
I've cleared down 2.7 Gb of software in readiness for a nice clean install.
Amazing how that stuff just piles up.