/etc/network/interfaces was the culprit. 18 seconds from boot only now (still no grub displayed though).
I used ADFENO/root_vegetable method to get ethernet up. I installed wicd. Job done. No more plain wpa_supplicant if I can avoid it. Thanks a lot for the help !I'll write down all I need for a super lean but easy to setup netinstall, and reinstall the whole thing, with the focus on grub.
