I'm not sure how much help I can be, but I'll give it my best shot--I feel like his speech pattern is one of those things you kind of have to feel out and experiment with until you feel confident! A friend of mine played a character a while ago that had a really bizarre way of speaking, and what she did was she broke down what kinds of phrases he spoke, figured out where they came from, and used that to compile a list of things he was likely to say; and I think something like that would also work here. Drippy has a welsh accent (If I'm remembering right, I could have that wrong), so I'd take the things Drippy says and use that find other phrases/slang that make sense for the character.

Something you want to keep in mind, too, is that you have to be careful when it comes to heavily accented speech patterns. (The best example of this I can think of is Bunnymund from the Rise of the Guardians, where people had a tendency to add too much slang to his speech). Drippy's speech pattern is really important, yes, but it's also important to balance it so it doesn't become overbearing and difficult for people to read.

I hope that helps! Also, I have an Oliver muse lying around, so if you ever need someone to help voicetest, don't hesitate to hit me up! There need to be more Ni No Kuni rpers in the world.