I've already changed my keyboard layout to English (UK) as per these instructions (Configure appliance for QWERTY layout (UK)). Every key is now correctly assigned except for hashtag, which on my macbook keyboard I can enter by pressing Alt-3. I've noticed that when pressing Alt in gedit it enables you to shortcut the menus at the top of the screen, so I assume Alt is just assigned to a more general function. I've tried going through Key Mappings (Preferences -> Keyboard & Mouse) but haven't managed to get this to work yet either. Anyone have any ideas?