i have to admit this is the first t.v. or film adaptation of a Christie
novel where i was confused by the ending. if i got the revelation
correctly there was no host and hostess who invited them and the whole
thing was set up by Charles Dances's character?
Yes. Actually most of the guests figured out the host and hostess didn't exist earlier, realizing that they were a front for the killer, but they couldn't figure how who the killer was.
In the TV version Blore saw Vera and Lombard making out and thought they were the host and hostess in disguise. That touch wasn't in the novel, because they never flirted in the novel.
You got it right. They first begin to figure it out when the initials of their "hosts" spell out "unknown."
Starman, waiting in the sky. He would like to come and meet us but he thinks he would blow our minds