Arrive at the door time shown on the KalaSudha event page. Doors open before the music starts, so you can find a seat and settle before the first note. All times are UK local time.
When the programme opens with a raga, the first section is the alap, the slow, free-tempo opening of the raga. Arriving after the start time means walking in during it.
For seating, see Is seating allocated? If this is your first Indian classical concert, read what to expect as a newcomer.