I have been wondering how people who haven't read the book have been doing because even I thought they'd rushed the prophecy a bit. There's just so much plot to fit in, and even though it is possible (as they are proving) to focus on t^he main story and ignore the footnotes, the footnotes add so much history and texture to the story.
The whole prophecy is very long but the important bits are:
^The nameless slave wore a silver crown
The nameless slave was a king in a strange country.^
and
^Two magicians shall appear in England.
The first shall fear me; the second shall long to behold me;
The first shall be governed by thieves and murderers; the second shall conspire at his own destruction;
The first shall bury his heart in a dark wood beneath the snow, yet still feel its ache;
The second shall see his dearest possession in his enemy’s hand.
The first shall pass his life alone; he shall be his own gaoler;
The second shall tread lonely roads, the storm above his head, seeking a dark tower upon a high hillside.^
For Lady Pole, the bargain was that the Gentleman got half her life. Norrell assumed that would mean she would die at 43, say, but actually the Gentleman took all her nights. She's going mad during the day as she's awake and dancing every night - it's sleep deprivation, really. The bargain never actually said "before" he takes her; he is just allowed half her life.
Drawlight and Lascelles (the two posh men hanging around) haven't been explained over well either, though they are fab. They were basically just aristocratic hangers on who followed fame and gossip. Lascelles is a rich playboy, Drawlight is a poor hanger on. They start to hang around with Norrell because they thought it would be amusing but soon see there is money to be made by becoming a sort of public face for him, and Norrell is so unworldly that he lets them.