And then select from that font table. Here's an article about this.
So open Font Book (http://support.apple.com/kb/HT2509 ) and then look at the Repertoire (displays all characters available in the font. You may need to use the scroll bar or zoom slider bar on the right side of the window to see all of the available character.)
Now that you know where it is in the Font set, you may be able to key it in. I did not find an "ASCII" font set.
Back in the dark ages, before most of you were nerds, it was possible to use (please correct) ASKEY to form characters using "Alt / 156" to get £. This I did on my iMac key board to save using the $ etc recently. I now find that the Shift / 3 key now prints £ instead of the Hash sign.
Any idea how to reverse it please?