Thanks. Thought it was worth asking before I did that, and yes the new kernel will install. If it's of use, this is part of the messages as the process completes:
Setting up linux-image-4.8.1-towo.1-siduction-amd64 (4.8-2) ...
vmlinuz(/boot/vmlinuz-4.8.1-towo.1-siduction-amd64
) points to /boot/vmlinuz-4.8.1-towo.1-siduction-amd64
(/boot/vmlinuz-4.8.1-towo.1-siduction-amd64) -- doing nothing at /var/lib/dpkg/info/linux-image-4.8.1-towo.1-siduction-amd64.postinst line 263, <STDIN> line 2.
The link /initrd.img is a dangling linkto /boot/initrd.img-4.8.1-towo.1-siduction-amd64
/etc/kernel/postinst.d/initramfs-tools:
update-initramfs: Generating /boot/initrd.img-4.8.1-towo.1-siduction-amd64
W: mdadm: /etc/mdadm/mdadm.conf defines no arrays.
/etc/kernel/postinst.d/zz-update-grub:
Generating grub configuration file ...