Changed the roof motor myself yesterday, don't know what all the fuss is about, took it steady, and now roof working fine.
The old one was soaked but even though I bought new sound deadening and housing, I could have dried it out and refitted saving about £60...
Sealed the new housing and made sure drain hole was clear.. £328 all in.
Two things to watch for, in Shipkillers guide it says you cant get the wiring connectors mixed up, but the motor cables and the heated rear window connectors, both fit each other, I know I tried it..
Oh and the new pump is stamped with numbers for the hoses, and these are marked back to front. Ignore the markings on the new pump and put the hoses on the same way as they came off the old unit.... or you will be taking it out again.....
Incidentally, removed the old motor from the pump and managed to kick-start it, cleaned it up and filled it with WD40, hasn't missed a beat in either direction since, so I have a spare complete assembly.
So if you are thinking of buying a Z4 and hear horror stories about the roof motors, don't let that put you off, I could have had it fitted for another £140, a service can cost more than this repair.....