A door opens in a tiny mews house in Notting Hill, west London, a stone’s throw from the tourists and antique dealers of Portobello Road market, and a familiar face appears. “Where do you want to do the interview?” Mitsuko Uchida owns two houses on this street — the one where she lives, which has a grand piano, and the one opposite, her studio, which has two grand pianos. “Normally people want to see the pianos,” she says, gesturing over the road. “Either way, whichever you choose, you will…