Soggy,
Hash, with the keyboard set up as a UK layout is alt-3.
If you go to System Preferences>International>Input Menu, you can setup your the keyboard of choice. In fact, on a Mac, it is very easy to mix different character sets, simply by setting the keyboard you require through a menu at the top of the screen. For example, if you wanted, you could have a page of text in Arabic, Chinese and Bog-standard English.
If you need to locate any characters in the particular font you are using, click "Keyboard Viewer" in the above system preferences panel. Make sure you click the "Show Input Menu in Menubar" option at the bottom. Close the panel and look at the right hand side of the menubar. There should be a flag of the keyboard currently in use.