Check the SRS loom connections at the seatbelt reels in both pillars first. And then all other SRS connection points.

Which model do you have. I had a 96 P Vitesse Sport for 11 years till recently.

Check 'clock spring' (behind the steering wheel) continuity second.

iirc Disco 2 uses the same clock spring mechanism (and has same stalks too).

These cars also had a common problem with dodgy connections in the fuse box which can cause all sorts of electrical gremlins. A friend of mine used to recon them and sell them on eBay. Find me on facebook using pcelectrics at aol dot com and I'll put you in touch and he can tell you what to do to check yours (assuming you can use a soldering iron?)