Just picked up the car, and works like a charm.
Ended up getting a brand new Bosch BXN1231 fitted for $400 from High Auto Electrical Service (27 Hope St Ermington 2115 NSW... 02 9874 4135).
The BXN1231 is what came on late model VL's and R31's, the earlier models came with the same Hitachi LR180705B... which is the same as the one on the cef. So it wasn't much hassle to change to the Bosch one, which comes with a one year australia wide warranty.
Urgh. Old man's insistance on fitting brand new parts as replacement sometimes amazes me. If it was me I'd have just chucked in a secondhand R31 unit for $50 in the backyard with a 12mm.