You Guys Are Smart, Right?

Time to pick your brains! How how well you google? ;)

I am writing a short romantic story for a friend of mine. I've decided (or the story demanded) that I go with ancient Britian.

Of course, that is so not my area of expertise.

I have the mythology all set for the story and I know I want it to take place after the fall of Rome. The mythology I am using is Welsh/Cornish so I am looking for names for people from anywhere from 500-1000 C.E.

Basically, I am looking for more historically accurate Welsh names. Am I correct that the people called themselves The Cymry at the time? I'm just looking for a starting place to get some names, mostly male. I've hit some places for some broad history but I'm stumped with names. Googling came up with some results, but I am not sure how accurate they are.

If any of you are familiar with that time period and/or names, I would appreciate it :) I'm writing a short story with a historical/time travel segment and I like to be as accurate as I can. :)