SRS on discovery TD5

HI everyone
I've just had my disco (TD5 facelift 53plate) MOT'd and have an advisory for the SRS warning light not illuminating is this an easy fix as I have had my motor for 4 years now and this is the first time I've had this advisory.
Any help would be greatly appreciated
thank you

Sadly this is a how long is a piece of string question.....

As it really depends on why the light isn't coming on.

Simplest fix will be a blown bulb. But I'd think this is highly unlikely. More likely is someone has tampered with it to stop it coming on, but that would then ask why? Such as, was it not turning off due to a fault or issue.

Really it'll need some investigation to see what is going on. Cheaper if you can do this yourself, else you'll be needing to pay someone to have a look.