Well, that was quite a dinner.
Had an interesting discussion about the different kinds of corks and screw caps as well as wax and foil. Conclusion was that, though they use natural cork at the moment, it is incredibly hard to maintain consistency, and so they're experimenting with composite and synthetic corks. They have decided that glass corks are unsuitable because the silicone fatigues over time and loses elasticity.
It'll be really interesting to see how the Old World wine industry changes in the next 10 years or so. I suspect natural cork will become increasingly rare on expensive bottles, though clearly it depends a great deal on consumer perception.