Oh, I enjoyed it. (I love the book, so didn't realise how confusing it was.)
It is all extra confusing anyway, because Dickens died before finishing the book, so no-one knows who killed Edwin (if anyone killed him at all), who Neville and Helena are, what all the fuss about the Lady Mayoress' grave is, etc etc. It's pretty clear who's going to marry whom, though 
Druggy choirmaster and squeaky clean vicar are just workmates. No-one at the cathedral knows how druggy the choirmaster is.
The Sri Lankan boy has come to be the vicar's pupil, to catch up on his education. There's some explanation for it which they've entirely left out - I think the vicar's mum is into good works, and an awful conceited philanthropist that she thinks the world of is in charge of finding the twins somewhere to stay in England. There's a mystery about who they are and how they're connected to everyone else. Probably their father and their abusive stepfather have something to do with it. Maybe they're Edwin's brother and sister or something.
Helena has been sent to the same boarding school in the town that Rosa is already at. Rosa has been engaged to Edwin for years, which gives her a status amongst the other girls.
Poxy hag is the opium dealer. She's got some concrete reason for thinking she can blackmail druggy choirmaster (I think she actually comes to the cathedral after Edwin disappears.)