I've already answered this question in private but for anyone else who was wondering. The obviously made-up names in the members list belong to spammers who've been banned from the board and had all their posts deleted.
So why are they still listed? This subject comes often up in Q&A sessions with the authors of the software which powers these boards and the official answer is "They are still members even if they are banned members" which is total cobblers to me but I'm afraid there is little I can do about it.
There are ways of deleting and blocking spammers totally from a board but they also make it difficult for genuine posters to sign up so that is not an option at present but the situation is under constant review.