I put my 2008 SE through it's MOT yesterday - it passed but the inspector made a comment.

The rear inner brake pads are warring faster than the rear outer pads.

Does anyone have an idea of why this could happen, and should I do anything to correct this ?

Inner pads are directly pushed on by the piston whereas the outer pads rely on the whole caliper sliding in it's retainer/carrier.
I would suggest you check that the calipers are not seized and lubricate with an appropriate brake caliper lubricant. MY15
Tyre Pressure Monitoring System (TPMS)
Surround Camera System
InControl Apps soon to be replaced with CarPlay (WIP)
Meridian Premium Surround Sound
Digital Audio Broadcast
Timed Climate
Cruise ECO Data
Follow Me Home Reverse
Extra Features Menu
Picture In Motion
4x4i screen (WIP)
Digital Broadcast TV
Meridian Rear Media with WIFI
Factory Powered Tailgate
Blind Spot Monitoring (BSM)
Reverse Cross Traffic Alert (RCTA)
Electrochromatic Wing Mirrors (WIP)

Ditto.

Often seen and the freer the caliper slides all the better. Clean up all the working surfaces and treat the slides with a limited amount of copper grease. A small (yes small )dab on pad seating edges is OK and piston face. FL2 MY10 TD4 GS traded in at 2 years
FL2 MY13 TD4 GS Current

Yes it's like most brake jobs, take it apart, clean it up and reassemble and everything works fine. 3 x FL1 2 manual + 1 auto
5 x FL2 4 manual + 1 auto
Now Discovery Sport P250 MHEV SE