- Low Interest rates
- Increasing National Debt (see: Why debt affects Sterling)
- (falling value of sterling)
However, the problem with quantitative easing is that increasing the money supply tends to depreciate the value of your currency. This is because it is less attractive to hold sterling if the value of sterling is going to be reduced by increasing money supply and inflation.
At the moment, the Bank haven't committed to quantitative easing - they will probably cut interest rates to 0%.
It is also worth remembering that although the Pound has weakened sharply against the dollar - to a low of £1 = $1.38, the US has already started quantitative easing, has a higher national debt, and their banking sector is just as fragile.