Apparently the new show is to be truer to Dickens' book rather than Lionel Bart's Oliver and early on in the series when research was done, there were a lot of Irish girls in London so the fact that Jessie is Irish is not relevant.
So we're to have a hefty Nancy - I hope the actor who plays Bill Sikes is a big man other wise how believable will it be that Jodie/Nancy would be beaten up by him and not give as good as she got. I just can't see her as vulnerable, abused Nancy.