That is the question for you.
The term head of state is often used differentiating it from the term head of government, e.g. as
in article 7 of the Vienna Convention on the Law of Treaties, article 1 of the Convention on the Prevention and Punishment of Crimes against Internationally Protected Persons, including Diplomatic Agents and the United Nations protocol list. For instance, in parliamentary systems like the United Kingdom of Great Britain and Northern Ireland and the Federal Republic of Germany; the Monarch and the President are recognized as their respective heads of state, while the Prime Minister and the Chancellor are recognized as the heads of government. So what technicality are you refering to?
http://www.un.int/protocol/documents/Hspmfm.pdf
http://legal.un.org/ilc/texts/instruments/english/conventions/1_1_1969.pdf
http://legal.un.org/ilc/texts/instruments/english/conventions/9_4_1973.pdf
Now you are saying United Kingdom of Great Britain and Northern Ireland(which is the full name for UK) does not exist technically? The roles of head of state in the other countries of the commonwealth realm are divided between the monarch and the governor generals. However technically and constituitionally the Queen only can exercise her power in UK but no where else. I have heard the dispute of whether the governor general or the queen should be the head of state, but this is the first time I have heard someone dispute whether the prime minister of UK or the queen should be the head of the state for UK.
And where do you conclude that Wales, Scotland and Northern Ireland are sovereign states same as other countries within the Commonwealth Realm?
Do you know why, if indeed, The UK exist as a whole sovereign country, why would there be 3 different team representing the UK in the World Cup? Instead of a single team UK?
And why do you think it is a team GB in the 2012 London Olympic instead of a unified team UK?
Scotland national football team - Wikipedia, the free encyclopedia
Wales national football team - Wikipedia, the free encyclopedia
England national football team - Wikipedia, the free encyclopedia
And do you even know there is a border between Scotland and England?
What you might perceive as the unified country infact were 3 different soverign, the situation of "the UK" is more or less the same situation as in Hong Kong, would you consider Xi-Ji-Ping as the head of states of Hong Kong or CY Leung as the Head of State of Hong Kong
While Hong Kong is politically independent (no rep from CPC) and autonomic, Hong Kong however is the soverign of China, but Chinese government have given the Hong Kong government highly independent political power to control their own government, beside military and foreign policy.
That is why there is a seperate team to represent Hong Kong rather than a single unitised team China
And while it
IS the president of China, Xi, is also the head of state in Hong Kong, technically it was CY that is running the show and Xi have no power over Hong Kong under basic law, does this situation sounded familar?
This is the last reply on this post, ME and YOU are saying the same thing, I don't really know why you still don't gets it, and I am starting got tired to find out why, if you still don't understand why, then I am sorry, I cannot further dumb it down for you, in term of governmental level.