Lysander definitely doesn't care enough to do accent work, so he'd woven a fantasy for himself that he's visiting from London as well. So the small scoff he gives is just at her ego, not her accent.

"Just don't slough any more of your money off on them. Movie stars have enough. I have an associate in Los Angeles." (People had associates everywhere in the olden times, didn't they?) "I'll give you his number for 100 galleons. Extra fee."

He is, he's decided, a very crooked barrister.