I wasn't aware of any other demonyms that add a V, except the unofficial Whovian (a fan of Doctor Who). This Wikipedia page turned up a few more more:
- Barrow-in-Furness → Barrovian
- Oamaru → Oamaruvian
- Oslo → Oslovian
- Peru → Peruvian
- Warsaw → Varsovian
- Waterloo → Waterluvian
Judging from the switch from W to V in Varsovian, I'm guessing this has something to do with Latin, but the places in that list don't seem to be linked by a Latin sphere of influence. Why do some demonyms add a V?