There's something funny about the part numbering on the ABS units. I think the complete unit has one part number, the hydraulic another and the module another. Most ABS units I've seen are listed by the module number not the hydraulic unit. Point is by searching for all 3 plus a less specific term like Z3 (or E36, E46 which share the part) you will get more hits and a better price. It should be possible to get a complete unit for under £40 unless it's a scarce type.
@DarrenS I will try and dig a unit out for you today but as I said before I am a slow coach - especially at the moment. Happy to send you the unit only for £27.50 including postage so bear that in mind regarding what you may otherwise pay. But that's if I have one and get a chance to look around.