Good news and bad news i suppose.... the good bit was that they "only" charged me £36. The bad was that they don't know what's up with it. Its got them stumped and they said they have never seen anything like it before on any bike. The nearest that have seen is when a race team removes multiple electronic parts from S1000's that they don't need. The bike tends to start shutting down other components that receive inputs from these removed items.
The situation now is that the fault code has gone away. It went after I hooked up a borrowed shock with a known to be good ESA motor (it didn't work with this either). However the ECU and my ESA motor still won't "talk" to each other. Bowker's said they never seen that before and in their opinion it could be a loom issue causing cross communication and confusing the ECU, which then stops trying to talk to the ESA motor. Fixing it could be ££££ while they run through the loom looking for faults. Err, no way - which they expected. The other thing is that in messing about with the ESA motor, specifically banging 12volts into it, I may have screwed it up. Other than that they couldn't suggest a way forward - oh they could but it involved giving them a signed blank cheque - a proper wallet hammering.
My options seem to be:
1. push 12volts into the rear shock motor and get it approx onto the rider+pillion setting.
Pros: Cheap. I still have ESA for the damping.
Cons: Risk of screwing up the rear ESA motor. I have to ride all the time with the bike on stilts - it would effectively be in the off road "high mountain" position as the front is already up. Resale value if I ever sell is seriously down (although by then mileage will be over 100K so probably not a huge impact on value).
2. Replace rear or both shocks with non-ESA Wilber's (or A.N.Other brand).
Pros: gets me adjustment for solo & pillion use albeit manually. I can offset the cost by selling the WESA shocks (still probably about £500+ to swap); I lose an electronic dooh-dah that is IME a weak spot. I get some brand spanking new shocks (again)
Cons: No ESA at all. Quite expensive. I lose an electronic dooh-dah that is a major feature of the bike; Resale value loss mitigated by still having quality adjustable shocks (some may see as a bonus anyway).
3. Do my own investigations into the loom and the ESA motor.
Pros: It might be cheap if I can find and fix the issue. I get a fully functional ESA system back.
Cons: Nobody is 100% sure its a loom or ESA motor fault. I don't really have the skills or knowledge or tools (a GS911 is not good enough) to do this properly (I have already just about exhausted my skills on this). Huge risk I screw up something else while testing circuits. I will probably need to buy a used ESA motor for testing, parts or as replacement when I completely screw up the existing one after taking it apart. Bike off the road for an extended period while I investigate Cost of electrical parts +used ESA motor may work out about the same as option 2.
4. Give it to an expert (BMW Motorrad or an independent) with the full diagnostic suite and the skills to rectify electronic faults.
Pros: It will get fixed. I get a fully functional ESA system back. If fault is easily and quickly found it could be cheap.....
Cons: .... but more likely could be hugely expensive in labour and parts.
5. Do nothing.
Pros: Cheap. ESA for damping still works. I have a good excuse not to take the wife out on the bike.
Cons: We use the bike a lot for UK and overseas trips two-up with camping gear. It really needs to be raised at the rear to keep the bike level, stop it from bottoming out and dragging stands and pegs on corners. Extended use this way likely to cause premature wear on shock and other suspension components.
At the mo my preference is option 2 replacing both shocks. Any thoughts?
Obviously the choice is yours, but knowing you I think you will take the right option. 
