I have no real first-hand experience of this other than a recent test drive. The test car had the sunroof and half way through the test drive, the salesman asked me if I'd ordered one on our MCS (less than 5 weeks to wait now!
). Once I had confirmed that I hadn't, he was happy to point out the steady woosh coming from above and admitted that they normally prefer an all metal lid on their demonstrators as it gives a better first impreession.
Not sure if this helps at all, but it does prove that dealers are well aware of this problem and that it is not uncommon. Whether it's a design or a build issue remains to be seen I guess - let's hope it's the latter as there's a bit more chance of it actually being fixable!