With the trim pulled away from the side of the boot, you get a good view of the metal bar that supports the two pumps and hoses.
The bottom end of the bar fastens through a grommit in the floor of the boot. In the image above you can see the bar exiting the boot floor, and also where the lower of the 2 pumps fastens to the bar, via cable ties (!! - nice work Alfa)
The top of the bar uses one of the studs that are also used to fasten the plastic covers over the rear of the rear lights.
The image above is a better shot of the pump arrangement. The hose at the very bottom connects to the water bag, from which it is pumped firstly by the lower of the 2 pumps, then boosted by the top pump and forced down the hose to the front of the car to exit via the nozzle infront of the intercooler.
So there we have it, a concise guide to the waterspray system. On the following page are some hints and ideas on how to get your waterspray system working