Does Scotland have an independent monetary policy from England?
No. Scotland and England are both included in the same economy. They are regarded as a part of Britain. Scotland does print its own banknotes though which are different from English bank notes but are equal in value.
The 'impossible trinity' is the combination of free capital mobility, a fixed exchange rate and independent monetary policy. Countries can choose any two of these three but achieving all three is impossible e.g. the UK has free capital mobility and independent monetary policy but a floating echange rate and China has independent monetary policy and a fixed exchange rate but restrictions on the movement of capital.
designed for the short term Keynes advocated that Fiscal Policy was a more powerful tool. this is mainly due to the fact that at the time he lived there were very few central banks that were truly independent from the government. The central bank had to be independent for monetary policy to function properly. Keynes did not address monetary policy and this is one of the main distinctions between him and Friedman.
The United Kingdom is comprised of England, Scotland, Wales and Northern Ireland. Each of these regions has its own local government and can legislate on most things except for monetary, military and foreign policy in much the same way that individual States within the United States have a degree of autonomy.