Since the Middle Ages a person in England has been prevented by law from doing as they wish with their own body. Then the crime of mayhem prevented people maiming themselves in any way that would leave them less able to fight for their country.
For this reason and to protect public health, so that bodies did not sit around waiting to be buried by families, English law has developed without allowing for ownership of a human body. Under common law, relatives were only given the right to possession of the deceased's body to dispose of it.
Cutting across this right to dispose of the body, the Human Tissue Act was introduced in 1961 to allow for the possibility of organ donations, but since then there has always been a shortage of people willing to agree to allow their own or their relatives' organs to be transplanted. Attempts at bringing in a presumed consent system have failed, despite succeeding in continental Europe.
Whereas the Napoleonic Code-based legal systems of continental Europe attempt to lay down everything you can do under the law, as well as what you can't do, in England, traditionally the law has been aimed primarily at telling subjects of the Crown only what they cannot do. As such there is great resistance to any law which states that a person will leave their organs available for transplant at their death. Needless to say, this culture is changing with the greater integration of the UK into the EU.