Norrell makes a fussy sort of flapping motion at Childermass, as if to silently communicate yes, yes, we'll get to that part.

"Can you not see the girl is distressed!" he declares, before moving on to the important (in his opinion) part. "Do you think they will come looking for you here? They cannot enter -- none of us would give them permission, of course! We do not allow their kind here!" Vampires, fae, all the distasteful sorts. "But it will be... difficult, if they linger."

Give a bad sort of impression to anyone who notices. Make it hard to leave if they haunt every doorway. His reputation may well suffer if his house is seen to be surrounded at all times by less than respectable folk!

Of course, it may suffer for harbouring a midnight witch too, but this has good reason! It is for a greater good!