@Scuba SteveActually turns out I have a BBS01 motor which every retailer barring Greenbike said couldn’t be fixed as parts were unavailable. Anna at Greenbike assured me that the ZE and LD gear were in fact one and the same thing, and only stamped differently for differently retailers. Despite being a little dubious about this, Anna showed me evidence that the workshop had in fact tried this and the motor runs perfectly on BBSO1/BBS01B and BBS02/BBS02b with either ZE or LD and I’m each model.
Received via Royal Mail 5 days and to my relief it was a perfect fit
Fitted mine yesterday and as you quite rightly stated, it's a direct replacement. I did notice, though not a problem, that the thread on the locknut side is a few threads shorter than my old axle. This meant that I could only fit the one nut and didn't have enough threads to fit the second locknut. Did you notice this when you fitted yours?
The drive is much much quieter now, I must have had a poorly machined original secondary gear.