Instead of just being rude at those opposing this, we should take on their arguments. Most of them are thumping the table and shouting about their rights, now "I'm not a lawyer" but I have read both the Universal Declaration of Human Rights and the Council of Europe's Convention for the Protection of Human Rights and Fundamental Freedoms and cannot find anything giving your corpse rights. You don't even have a right to be buried although in this country there is probably some clause in one of the Environment Protection acts that makes your local authority do something with otherwise undealtwith bodies, to stop them making to much of a mess.
While the old legal position boiled down to the old quote
By the common law of England a corpse is not the subject of property nor capable of holding property. It is not therefore larceny to steal a corpsemuch was changed in the aftermath of Alder Hey with the Human Tissue Act 2004, but given the list of people who can consent to chopping you up is 14 relations long with a "friend of longstanding" tacked on the end it probably isn't really that difficult to get on with the scalpel. As with much modern legislation built in is the concept that everything is governed by code of practice enacted by the Secretary of State so there may not even need to be primary legislation to bring about the change in the consent methodology.
As an aside, while reading the act, I noted that breaking the law on live organ donation is only subject to a maximum of 51 weeks in prison!
 Although I would like to be, probably not practising, but if I did have 10 grand knocking about and more free time and OU law degree is very tempting.