Some research conducted and hopefully this will help. As
@skny stated, the mirrors/reflectors/bowls degrade over time. These are meant to have a mirror finish but wear and tear results in the finish slowly becoming less and less reflective (as illustrated below):
As you can see what we want is the reflector to look like the one on the left, however in reality on early 197s which are near enough 16 years old now, the reflector on the right is what we most likely have in our vehicles.
The issue is further compounded by the fact that the actual lenses can also become dirty with deposits, further reducing light output (as seen in the below video).
So what are our options from here?
1. There is a gentleman in Poland who can refurbish the reflectors or provide ones on an exchange basis for a very fair price (as well as providing other services):
https://regeneracja-hc.com/reflektory/renault-clio-iii-2005-2012/
2. Attempt to remove the reflector and lenses yourself and clean them/refurbish locally.
3. Potentially purchase a set of new projector units and transfer the lenses/reflector into your Xenon units. I suspect they are the same between Projector and Xenon headlights (but cannot guarantee it!)
4. Purchase a set of new projectors units (lenses and reflectors) for Xenon headlights:
https://retrofitlab.com/products/renault-clio-3-2006-2009-bi-xenon-xenon-headlights
I should also add the inclusion of the video above is not a recommendation on how you should clean the lenses. There are conflicting views/opinions on how it should be done (distilled water/ammonia vs. contact cleaning with IPA), so you'll need to research and decide upon the best method of cleaning.
