UPDATE: Turns out its not actually a fault.
After some in-depth reading of the manual, it seems that the indicators will only flash if you have a "security system" installed.
Seems kinda silly to me - surely you'd want to know your car was locked whether you have a security system or not.

As well as the indicators, those of you with security systems will also see a red light flashing below the instrument panel.
So that's that little mystery solved.
I'm going to have a look over the schematic diagrams to see if there's a way to make the indicators flash anyway.
If anyone else is unlucky enough to be without one of these "security systems", I will post back any positive results.
Thanks to anyone that tried to help
