Update on the seat situation: I purchased a new lever for the driver side and had a go at replacing it yesterday. I immediately realised how fiddly it was to separate the head rest elbow without chewing up the plastic with my flat blade in the process.
Following in the guide on E31 FAQ was simple enough and I managed to remove the lever only to find that I already had the reinforced version! ('tis a 99 model I guess) This lead to further investigation and I removed the seat back for a poke around. What I've noticed is that no matter how much pressure I exert on the actuating arm it won't pull the cables through and I reckon that the problem lies at the other end of the seat cables.
Can anyone confirm that the end of the bowden cables are situated underneath the seat base?
With the seat back off it gave me an opportunity to familiarise myself with the electric motors and gearboxes prepping myself for 'surgery' on the height adjuster. Am I right in thinking that the motor for this action is also underneath the seat therefore requiring me to remove the seat from within the car in order to rectify?
Also, do I need to disconnect the batteries prior to seat removal so as not to set off the airbag light?
Thanks!