Respectfully, I think you'll find that is wrong..
Humans have been moving toward individualism since ancient times. the drive has always been for greater autonomy, for the individual, the group.
But what sized group? A family, a village, a nation? Put another way, how much should we split the UK up? NI, Wales, Scotland, England? Should England split into North and South? What about Cornish Independence? Some in Northern and Central Wales feel that the Southern coast of Wales isn't properly welsh, Should Wales split up? Do we go back to a pre-Roman set of boundaries?

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I'm not trying to take the p, I'm trying to see where you think the level of "nation" should be set.
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Unions exist for the purposes of defence and economics. The UK was created as a defensive organisation at a time of an increasingly belligerent France. The Union with Ireland came into being directly because of the French Revolution. The fear being that, with improvements in naval technology, an Ireland, occupied by France or any other belligerent European state, could threaten Great Britain. That was the purpose of the Union of 1799.
Those threats no-longer exist. A military union with Europe, which is happening progressively now, is in the best interests of all of the states of the UK.
So the UK Should be disbanded, but the remaining States (however sized) should integrate more closely with Europe? Have I got that correct?
The economics of the England Scotland union were that the Scots business experience was introduced into the management of the English empire creating vast wealth. It is particularly interesting that the wealth of the empire increased even more with the abolition of slavery, allowing those previously enslaved people to contribute as individuals, that than as someone else's property.
Not going to disagree with the abolition of slavery!
The economic value of the UK union is now gone. The economic contribution of London, while initially affecting London and its surrounding counties, (where I live for example), is European, even world wide. It is the nature of the economic success of London that it is, necessarily, international.
Whilst I agree that the success of London relies on it's "internationalness", I would disagree that the value of the UK as an economic unit has gone. Personally, I believe that (where economies are involved) there are advantages of scale. This extra size allows for things that are impossible for a smaller economy, like a space program.
Self determination is the aspiration of all peoples. You seek to think for yourself as do most people. We all seek to avoid and detach any aspect of outside control.
Yup, but how do you define outside control. At the moment there are things I cannot do because of the outside control of the parish council. There are things I cannot do because of the outside control of the county council. National (England and Wales) laws also affect me (say when I sell a house) and UK laws also impact me (say the national speed limit or requirements for a driving licence). If I were to commit genocide, then international laws might also control my actions (don't worry I'm not the genocidal type!

). At what point do we say "these restrictions are not OK because they are imposed by outsiders"
The problem with the current arrangement, as illustrated by the proposals from the UK Parliament for expansion of the Scots Government's authorities, is that they are principally concerned with protecting their own interests. They retain control over key issues that could conceivably affect them at some time in the future.
There are clearly some issues with the status quo, and almost certainly some issues with the new powers devolving to Scotland. On the one hand some down south will feel too much has been given, and on the other some Scots will feel too little has been given. It is an impossible situation to solve.
The problem is further exacerbated by the resentment that is being created in England especially, over how much Scotland seems to have gained. We appear to continue to be subject to the UK's authority, having our lives governed and influenced by people whose interests are not ours. We have been promised high speed rail links for many years, yet all the effort and investment is being ploughed into projects elsewhere.
But that is the nature of Government, the interests served will not always be ours. To take your example of high speed rail, it may be for you (pure speculation here btw) that HS2 will be a fantastic advantage, allowing you to visit your mother in Birmingham very quickly (again speculation). If HS2 doesn't happen then that is the government serving interests other than yours. but for someone whose house/farm is being demolished/cut in two, by HS2, pushing through HS2 would be serving interests other than theirs.
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As I said earlier, the job of government is to arbitrate between it's citizen's sometimes competing needs. This means a Government is always going to go against a section of it's citizens needs sometimes. Ban foxhunting, appease the anti hunting lobby, displease the pro - hunting lobby. Legalise cannabis, please some, displease the Daily Mail. etc.
These are not necessary or acceptable compromises. No-one is benefiting. We are all paying an enormous cost.
Again, the acceptableness or otherwise of a given compromise, is a personal view point. For someone, it may be totally unacceptable for any animal testing to happen, full stop, end of story. Therefore it's continuance is not necessary or an acceptable compromise. For someone with a vested interest (say Parkinson's) who believes that some animal testing may provide a benefit to them and are happy that some animals are sacrificed on their behalf, banning animal testing is not necessary or an acceptable compromise.
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Anyway, given that you are not a fan of the UK as it is now, would you be more amenable to the UK as I proposed it? Are the Union powers too much, what powers would you put towards the union that you would find acceptable? I am genuinely interested as you represent someone who (forgive me if I'm wrong) seems to see no redeeming features to a 4 nation union at all and as such offers a useful insight into where a compromise could be drawn.