I may have written this elsewhere before, and its starting to feel a bit "ranty", so sorry in advance
The OEM Xenons use two different approaches depending on manufacturer. Either a mechanical lens that slides over the bulb (Bi-Xenon) to create two different beam patterns combined with projector lenses tuned to the optimal viewing distances or additional halogen bulbs for main beam (not so much these days).
Without the projector lenses, the beam strength is too much for a standard reflector to handle and as such it creates a very uneven, uncontrolled light output. Too see how this looks to other drivers, go get a really powerful torch, preferably a mag-light with 9 d-cells in it, turn off the lights, count to 60, point the torch at your face (close up), and turn it on. You now know how the person driving towards you at night feels. Alternatively, go find a supermarket car park at night, park near the entrance and wait for the local corsa crew to turn up with their aftermarket 55w 8000K Purple HIDs installed.
In the case of our cars the main beam and driving lights are separate units so it cannot be achieved as an after-market upgrade without cutting open the headlight and adding a new assembly to replace the the main beam reflector unit with a projector lens and the mount for a H4 type mechanical HID bulb. You can buy "globes" which are a HID mounted in a projector lens, that can be placed in a normal H7 bulb holder, but again, you need to take the headlight apart to fit it and our headlights are sealed with a glue stronger than the actual material used to manufacture the headlight itself, so good luck
Xenons are not suitable for repeatabley being switched on and off in short bursts, either as a warning / signal flash or for short stints while driving (main beam use). This is down to the fact that HIDs draw a significant amount of amps on start-up while they create an electrical arc in the bulb that heats up and melts a salt/crystal solution that turns to gas and makes light. This process is why they seem to "warm up" and take a short while to get up to operating temperature/light output.
Repeatability turning them off and on for short periods will destroy the bulbs, ballasts and maybe even the electrical circuits that they are connected to.
Remember, when Alfa designed the lighting circuit for your car, they worked on the principal that 2 x 55w halogen bulbs (4-5 amps each) were attached and not 2 x HID Ballasts that can draw up to 6-8 amps each on start-up and run at 4-5amps drain when at operating temperature. This is also why a replacement xenon headlight is 3 times as much to buy from a parts dealer as your standard headlight.
Dont get me wrong, this is just advice, your more than welcome to put HIDs in your main beams, but at the very least put a set of Capacitors on them to take some of the strain out of your lighting circuit