Spent a couple of hours addressing this today. First off I checked the boot light connector. 12v present but no continuity to earth - very likely the left-hand soft close loom identified by others on this thread. Stripped the boot lid down, stripped the insulation back and...bingo!
Black wire was broken, green came apart with the lightest of touches, blue was good albeit exposed:

Right-hand loom didn't have any broken wires (yet) but was deteriorating:

Soldered up the left-hand wires, insulated with heat shrink and relooomed with fabric tape:

On the right-hand side I just insulated the exposed wire with electrical tape and reloomed:

Put it all back together, worked a treat
Took a couple of videos from inside the boot of each latch - you can see how the loom moves when the boot opens or closes.
LH latch:
z4 boot left by Ian Conuel, on Flickr
RH latch:
IMG_1265 by Ian Conuel, on Flickr
Fingers crossed that my repair lasts :?
Have to say what a great resource this thread (and forum) has been. Would have taken quite a lot longer to trace that without the help of fellow owners
:ilz4f:
Black wire was broken, green came apart with the lightest of touches, blue was good albeit exposed:

Right-hand loom didn't have any broken wires (yet) but was deteriorating:

Soldered up the left-hand wires, insulated with heat shrink and relooomed with fabric tape:

On the right-hand side I just insulated the exposed wire with electrical tape and reloomed:

Put it all back together, worked a treat

Took a couple of videos from inside the boot of each latch - you can see how the loom moves when the boot opens or closes.
LH latch:

RH latch:

Fingers crossed that my repair lasts :?
Have to say what a great resource this thread (and forum) has been. Would have taken quite a lot longer to trace that without the help of fellow owners
:ilz4f: