Call this fella named Rosdi at 016-6565391, he's located in Sg Buloh. He has 13 years experience with Hotbits/Speedworks, assembling/servicing/repairing coilovers. He's now out on his own. He does repair/service/sell all types of coilovers.
He modified and serviced my E60's Bilstein B16 with ride control. However, the ride control mechanism couldn't be used anymore (had special magnets, couldn't fix), so he modified my B16 to an equivalent B14 spec, i.e. no more ride control,just height adjustable, no longer damping adjustable but it works and works well. He had to change a couple of shafts so overall price depends on whether have to change the shafts or not.
Note: luckily enough, i kept my original shocks and springs so i had them reinstalled while i sent my Bilsteins to Rosdi. Bear in mind that he has to go out and find the oil seals, and other parts so the timeframe to service the coilovers can take a while. My coilovers were sorted out in a week and i had to find time to reinstall the coilovers and redo the alignment again.
Hope the above info helps.