If Scotland votes for independence, the UK wont exist anymore, as the United Kingdom refers to the political union between Scotland and England/Wales. Therefore, the argument that Scotland will have to renegotiate with the EU, while the remainder of the UK will remain in the same deal is not correct. There will be two new political entities - Scotland and England/Wales/NI. Either negotiations will have to take place between both with the EU, or the EU will allow both parts entry under current arrangement.
And to be clear, this is about the end of political union, nothing else. All this discussion, and argument, in this thread about the difference in cultures is totally unnecessary. Scotland is being given the opportunity to choose its own political path. And politically we are quite different to the rest of the UK, England in particular. Scotland is primarily a socialist-voting country, left of centre. England on the other hand leans more towards the right, hence the current Tory government (and the only other viable alternative being a more and more right-leaning Labour party). This is why devolution has been good for Scotland - despite these parties being in power at Westminster, we've been able to maintain social policies in the areas that are devolved because we can vote for a socialist party in Scotland even if the choice is not available to us in Westminster elections. And this is why we have what some see as the unfair benefits of free education, a healthy NHS, free prescriptions etc. It's not because of an unfair distribution of money, it's because of a difference in policy. Meanwhile the Tories are hiking up tuition fees for those south of the border, privatising schools, privatising the NHS, talk of privatising major roads. This is why many people want independence for Scotland. The areas that aren't devolved are currently in Tory hands, and Scotland in general does not like Tory policies - we have only one Tory MP in Scotland. It is unfair therefore that Scotland should have to put up with them. What's more, the Westminster government currently has the right to take back any devolved powers at any time they see fit, so for Scotland to truly be governed in the way its people want, independence is the only certain way of achieving it.
Devo max seems to be a popular idea in Scotland, where all but defense and foreign affairs are run from Scotland. Effectively all money earned by Scotland remains with Scotland, and a lump sum will be sent to Westminster to pay for defense and foreign affairs. I personally don't support this because I detest the way Westminster uses these powers for nuclear weapons, illegal wars and unnecessary meddling in other countries, and believe a Scottish parliament would spend that money far more wisely. But to reassure those who are shouting about how unfair it would be if Scotland gets to choose devo-max without consultation with the rest of the UK, and that it's all-or-nothing, in the unlikely event that devo-max was to appear on the referendum (and it almost certainly wont), the Scottish government does not have the right to declare devo-max, it would only demonstrate the desire for that from the Scottish electorate, and would give the Scottish government a mandate to try to negotiate a devo-max settlement with the rest of the UK. So no need to worry there.
The Bank of England is an independent identity. It does not belong to England, it is simply a machine for controlling the pound. Scotland would have every right to continue using the pound if it became independent, and no political party could prevent this. The Bank of England could refuse if they felt that having Scotland use the currency would be a detriment on the pound. This will never happen, it would weaken the pound to remove Scotland, especially considering the money and stability that North Sea oil provides. The Bank of England is a shared asset of the union, and upon independence, Scotland owns a share of that asset (as it does all other assets, and of course the national debt). There are plenty of examples of currency unions - the Euro being an obvious one. It's also true that Australia and Ireland both kept the pound for many years before creating their own currency, and there were no issues with that, so why should it be different with Scotland?