Sad to say, this didn't work.
I altered the GRUB_CMDLINE_LINUX_DEFAULT line in /etc/default/grub from
and ran update-grub (and rebooted).
acpi appears to be running on the laptop:-
jeremy@dalek:~$ acpi -V
Battery 0: Charging, 95%, charging at zero rate - will never fully charge.
Battery 0: design capacity 2000 mAh, last full capacity 2000 mAh = 100%
Adapter 0: on-line
Cooling 0: Processor 0 of 0
Perhaps I should just write a suid script?