Thanks, I got it working although for some reason the postinst script in the uim package failed to run, saying it can't find gtk-uim-update. Don't know why as gtk-uim-update was installed to /usr/local/bin, which is on my path, and running it by hand worked.
I have to start uim-toolbar-gtk-tray manually in order to change input methods in leafpad. I like leafpad just fine, it isn't too big.