For any nation that splits and loses an essential component of its economic sector, faces the threat of harm to their currency. The Scottish independence would certainly harm the British Pound as it would negatively impact British economy. This has already been proven by Pound sinking to its lowest value in 10 months in the aftermath of mere opinion polls which revealed a majority of support for Scottish independence.
The pound will temporarily be harmed if Scotland seeks an official split. This will also challenge Europe's economic recovery as they seem to be getting back on track. There is no doubt that the British pound will suffer, if today's British market is any indication (pound fell by 6% in the British markets from the Scotland news). How long the harm lasts to the pound is anyone's guess and if Scotland is able keep the pound from a messy separation, may factor in varying results, but for now, Scotland seeking a spit certainly has everyone on edge and the pound taking a beating.
In fact is Scotland were the leave the Commonwealth the value of the British would likely improve. Since it is estimated that Scotland would take on 5-10% of the current Great Britain public debt. So the debt-revenue of the United Kingdom would improve as well as lowering it cost of borrowing.
If Scotland were to split from the UK, it would not harm the British Pound. This is because the world economy would react to the change within a few days and then the value would return to a normal level. Scotland is not a troublesome country and the change wouldn't be because of war. So the harm would be non-existent.