"Hash" key? It should be directly above the "3" on the row of numerals on your keyboard, if you mean "#", but I suppose in the UK it may actually be the pound sign.
oh right ok thanks. Im not infront of the iBook now to test it but I know that it is not listed on the "3". I will try when i get back from work and yet you know .
I think if you are on 10.4 then you can see all the little key strokes combinations by first launching System Preferences->International Pane and in that select the Input Menu. Then select the country you are from and select Character Palette & Keyboard Viewer. also select at the bottom of the pane "Show input menu ...". This will put you flag in the Finder left top menu. Once that is there, use the drop down to "Show Keyboard Viewer". Then Keyboard Viewer will pop up and you can see all the keys you type. Experiment with the shift and Option and Apple button with keys. You then will see in Keyboard Viewer all the key combinations.