LONDON — Orlando Bloom will make his West End debut in veteran Brit playwright David Storey’s 1969 drama “In Celebration.”The play, a Chekhovian-style ensemble drama about three brothers returning home for their parents’ 40th wedding anniversary, will be directed by Anna Mackmin and produced by Sonia Friedman. Dates and theater are still subject to confirmation but the most likely venue is the 380-seat Trafalgar Studios for a July opening. No further casting has yet been confirmed. Bloom has been eyeing legit projects for some time. He is keen to be part of a stage ensemble having worked exclusively on screen since being cast in “The Lord of the Rings” trilogy almost immediately on leaving London’s Guildhall School of Music and Drama in 1999.