Is there any way of getting rid of the default "Goodbye" dialogue?

I've made a new dialogue option and ticked the checkbox Goodbye checkbox however now I have my Goodbye dialogue ("I've got to go.") and the random default goodbye dialogue the game gives you. (Which is also voice acted by default voice overs, which I don't want.)

The only way to get rid of this is to create your own voice type for the NPC. This however, also gets rid of ALL the dialog. Including the things they yell in combat, if your stealing, shoot near them, or assault them. Just make a new voice type called like Male/FemaleUniqueMyCustomNPC then give your character that voice.

That's exactly what I was looking for, funnily enough I just thought about doing that as soon as you replied. Thanks for the response!

While I'm here, is it possible to use the default NPC voice overs for custom NPC dialogue?

Sure its possible. How do you want it done? Are you looking for the random things they say, like when the player bumps into something? Or are you looking to reuse actual dialogue in a different circumstance? There is a trick to it. Every time you make a new line of dialogue, the game automatically creates a default file name in a default folder that you cannot change. You can, however, extract the voice files then rename and place them into the proper folder that the Geck defines for you. If you double click on a topic info, you can see the required file name and folder path in the Audio section of the 'Edit Response' popup window.

In short yes - for the topics the NPC will automatically engage in due to faction/voicetype conditions, like combat, random chats, greetings, etc - your NPC will automatically pick that stuff up if you set it up right.

However, the second you create your own topic that you expect the NPC to use, you must create a brand-new voiced .ogg file and the .lip file to go along with it, and ship it with your .esp. Even if your NPC is saying a line that already exists in the game, you have to extract the .ogg out of the guts of the game, and pop it into your own .bsa or directory structure.

Time to get digging! Thanks a lot, you've all been really helpful.