The original thread that got me into doing this is here
The Z8 Chrome Washer jets are sold seperately at £22.61+VAT (so order 2, same both sides

Part number B61.66.8.380.122
Dealers will probably not have them in stock (not much call for Z8 parts) so they will order from Germany, payment in advance, delivery taking less than 7 days.
Here is a Z8 washer jet
First job is to remove the sound proofing under the hood to get access to the original washer jets from underneath. These simply unscrew (don't unscrew all the way out) and then pull out with the socket which is now loose in the hole.
You can now get access to the washer jets.
Next unclip the electric connector (for heated washer jets, standard on ///M but you may not have this on yours, the harness can be purchased seperately to add this function connecting to washer bottle connector - see original post linked above for more info). Also pull off the water hose. This has a metal clip, I managed to remove one side with the clip in place but the other I had to "unclip" with a small pair of pliars and reclip later.
Now you can remove the original washer nozzle. It needs to be released and pushed up through the hole. To do this you need to push the unit towards the front of the car whilst pushing up. Its pretty easy to release and I used a plastic stick as I have chubby fingers

You can then push through the hole
and remove from the top of the bonnet
Side by side you can see the differences between the two units. You can see that the connector for the water hose points in a different direction on the Z8 one. This did not cause a problem for me as the existing hose had just enough slack to reach the new position.
The main issue is that the part of the nozzle that "retains" the unit in place is very slightly different on the Z8 unit. This means that when in place the unit is not held firmly in place. It is secure but you can move it about slightly and its slightly lifted from the paintwork.
This was solved in the USA with a special retaining clip which "took up the slack" but this does not seem to be available any more

I did contemplate using black silcon sealent to fix in place (as this would not damage the paintwork) but decided on a neater (from the top side) solution which may / may not work. It is not very cosmetic from underneath but is covered by the soundproofing. I used electrical tape to "strap" the unit, effectively pulling the unit into the hole. This worked better than expected resulting in the nozzles being rock solid and a nice neat finish above.



With sound proofing back in place this solution is invisible
It will be interesting to see how permanent this solution proves but it will not cause any damage if it does not last and I can try something else.
I would be interested to hear how others who have done this conversion solved this.
Here is the finished results. I obviously had to adjust the water jets with a pin in the normal way but end result looks great with strong jets of water in perfect spots.
Time to do approx 45 minutes, fiddliest bits were removing the water hose clips (if you have to) and "securing" the units in place with tape.