The actor will appear in The Best Exotic Marigold Hotel, which also stars Judi Dench, Bill Nighy and Dame Maggie Smith as residents of an elderly nursing home in Bangalore.
Language and diction expert Vidur Chaturvedi told Hindustan Times: "I had a 20-day session with him in Jaipur. He's a focused actor and grasps lessons quickly."
Sources added that Patel's girlfriend and Slumdog co-star Frieda Pinto had turned up on set to help the 21-year old actor pick up the "desi" English accent.
The two have been dating each other since they first met on the set of the Danny Boyle film in 2008.
Indian-born Pinto recently said that she has no plans to work with her boyfriend again because they would not be able to capture their initial chemistry.
The Best Exotic Marigold Hotel, helmed by Shakespeare in Love director John Madden, is due for release later this year.