I found that it is far easier to abandon the small partition and move /boot to the root. This also prevents any out of space issues in the future.
First move your data from the boot partition to root (run as sudo -s):
cp -a /boot /boot2
umount /boot
rmdir /boot
mv /boot2 /boot
Remove (or comment) the /boot entry in /etc/fstab:
vim /etc/fstab
Update grub and make sure everything is correct:
update-grub
apt should now be able to upgrade without problems.
This leaves an unused 200mb partition (which you could use for something else if you find it worth the trouble).