It’s the same guy. Matthew Woods is his name, I believe. He voiced both the droids and Grievous in TCW and Grievous in Episode III. Not sure if he voiced the droids in III, but he might’ve.
Ah yeah, I did use some of TCW Grievous dialogue in ep3, but I’m not sure if I’ll keep it as it sounds a bit too different from the ep3 dialogue. Though I guess that’s more due to how they altered the voice, rather than the voice actor.