Yes, there is quite a number of Milliwaysers and ex-Milliwaysers that have published fiction.

I could now, theoretically, pick up one of my own characters from these short stories as a charrie, but it wouldn't be fair. Also, as I they're both contributions to anthologies of that shared world, they'd be Wraeththu, so they'd spend much of their time explaining to people in Milliways what that is, which could get boring rather quickly. So, no.