When creating new accounts, selecting the currency is very tedious (I have a mix
of Euros and Pounds). The drop down contains many currencies. One way to improve
this would be to repeat those currencies which have previosuly been used at the
top of the drop-down menu.

What I would actually suggest however is that the "New Account Default Currency"
preference option be removed and the currency when creating a new account would
come from the parent account. The parent account and currency are actually
selected in the same dialog so this will need a bit of interaction so a manually
selected currency is not affected by a change to the parent. It might also be
wise to move the currency selection below the parent selection in the dialog.

In allowing a preference option to be removed, this also has the benefit of
marginally simplifying the preferences.