Here are some suggestions, and my choice is bold. But I haven't got a good suggestion for Jonathan Strange himself, following adverse comments on Hugh Laurie :-) He has to be neither young nor old. He must be charismatic but not beautiful, active but bookish, and as coalescent says, 'intense'. Hmmm. Gary Oldman possibly?
Fairy King - definitely Jude Law. Some on the discussion board suggested a woman actor - which isn't a bad idea either
Norrell: pedantic, self centred, non-empathic, non-charismatic. But paradoxically, must be played by a marvellous charismatic actor. Derek Jacobi, Anthony Hopkins, Jonathan Pryce, Ian Holm
Childermass: dark, scruffy, brooding, working class, clever, maverick. David Thewlis I think would be the best, but when I was reading the book I visualised him as Alan Rickman
Vinculus - an alcoholic degenerate, the Frank Gallagher of the 1810s, has to be David Threlfall
Stephen Black. There are many talented aristocratic young black actors in the RSC and elsewhere. For instance David Oyelowo. And I'd like to see English actors in this film. But I have to think there is nobody as good as Denzel Washington for this role. I'll tell you why, Washington does that thing where his face goes polite and reserved, but you can see his thoughts working away below the surface, and that's just right for this role. Well, that is the role basically.