The Union Jack stays!
The United Kingdom of Great Britain, Scotland, Wales and Northern Ireland uses as its national flag the royal banner known as the Union Jack or Union Flag. The current design of the flag dates from the union of Ireland and Great Britain in 1801. It consists of the red cross of Saint George (patron saint of England), edged in white, superimposed on the Cross of St Patrick (patron saint of Ireland), which are superimposed on the Saltire of Saint Andrew (patron saint of Scotland).
It is interesting what will happen to the Union Jack when the voting of Scottish independence happen this week.