LONDON — Victoria Alvarez is a ball of energy, darting around the Seven Sisters Indoor Market in north London.

On a recent morning, she broke away from chatting with a friend to burst into a general store in the market, asking its Iranian owner if he had some supplies she needed. She barely had time to hear his response before she was off again, standing behind the counter at her currency exchange and parcel shipping stall. In a brief quiet spell, when her husband took over, Ms. Alvarez walked across the hall to one of the market’s hairdressers for a blow-dry.