Thanks for the quick replies! I love that I run Sid (on 4 machines), only notice something worth reporting every 2 years or so, and get immediate responses! <3 Debian.
I've not built a Kernel (or any related part) in a VERY long time, I think maybe 2.6.something? I've simply not needed to. I still don't need to :-)
I'm aware of the need being only for kernel headers, however I've been burned on Sid before by not grabbing them at the time of the image, and not being able to grab them later as they are not persisted in parallel in the repo. Then you're forced to get a new kernel and headers, and back then, that meant possible bugs/changed behaviours that I didn't want. So I always install headers up front. And I should use meta packages to do that, but haven't been in the past.
Meta-packages that glue this stuff all together seem to be missing from experimental too. If you don't care, it's fine by me. Just letting you know in case it was an oversight.