No, there cannot be more than one of ex-flatmate. There just can't.

I don't think that he's stalking me, or even knew that I lived in Welly. I just bumped into him on the street, and unbumped as quickly as I possibly could, while parting with minimal information about myself.

I do think that theres a good probability that most of his human interactions are pretty similar to the ones he has with me, and that he just doesn't know any better.
I feel sorry for him, but it's not my job to sociallize him.