In addition, Margaret is starting to feel a bit hemmed in because, in cosmopolitan London, she actually has less freedom than she did in the northern factory town. Her aunt would be scandalised if she walked anywhere, let alone to a working class area to visit friends. For that matter, Aunt Shaw would be even more scandalised by Margaret having friends among the lower classes. In Milton, the lines between social classes were a lot blurrier due to the industrial revolution bringing about social mobility. The Hales could employ Mary Higgins to help in their kitchen, and no one would think it remarkable that Margaret would call on the Higgins family socially as well. This would never happen in London, where one didn't even take notice of one's own servants unless absolutely necessary.
Mr Bell of course takes a lively interest in the man whom he suspects Margaret might marry and attempts to draw Henry into conversation when they leave the Lennox's house. Henry's comments are very illuminating, both to Mr. Bell and to us; it is clear that he has no respect or patience for Mr. Hale's having left the ministry because he had developed doctrinal differences with the Church of England and felt that he could no longer preach what he now didn't agree with. While Mr. Bell regards his late friend's actions as principled, Henry believes that it was the height of folly to give up a secure and steady income over some religious scruples. He backtracks a little when Mr. Bell expresses his displeasure, but when Henry compares Mr. Hale to Don Quixote, it's obvious that he regards him as little more than a misguided and naive fool.
When Margaret turned down Henry's offer of marriage, he retreated behind his usual mask of cynical ennui, something she found completely off-putting. Mr. Thornton's reaction to her refusal of his proposal was considerably more passionate: he was hurt and angry and showed it. Unpleasant as this reaction was, Margaret found it an easier one to understand than Henry's studied indifference.
It may be doing Henry Lennox a disservice, but one gets the impression that he is helping with Frederick's case with the idea of currying favour with Margaret in the back of his mind. As we learn from Mr. Bell, in Milton Thornton is exerting himself to help get Margaret's affairs settled there with no expectation that he will ever see her again, or that she will even know of it. It is simply something he can do to ease Margaret's burdens, done because of his love for her and also because of his friendship with her father. This is another fundamental difference between Lennox and Thornton: John could disagree with and debate Mr Hale- and did- but retain the highest respect and liking for him. Henry, on the other hand, saw Mr. Hale taking an action that he would never have considered and thereby concluded that the former minister was a fool, regarding him with mingled pity and contempt.