Hi Shashi,
I had the similar problem abt couple of years back. The custom people spoke all the rules in the book. I went to the Addl Commissioner of Customs, chennai and argued that the CD's were absolutely free of charge and that has no implication of any duty charges.
I won the battle and got the CD's about 15 days after the SFD 2006. In that process, our custom department people have lotted 2 T Shirts which i supposed that has been couriered to us by canonical.
My Humblest suggestion is that, please give a try in getting the CD's, as returning it may have costing parameter to be paid by Canonical. In this process we can show our courage of battling corruption and imagine how much work would have gone in for Manufacturing and shipping the CD's to us from cannonical.You have to pay absolutely nothing for getting that CDs.Please dont give up the fight for your right.
I have got nearly about 500 Cds and was told by the post man to pay the custom charges , eventually be waived off by the customs.
Regards
Thyagarajan Shanmugham