You might consider the New Zealand author Ngaio Marsh. She wrote her Detective Alleyn novels from 1934 all the way until the year of her death in 1982. Alleyn was a detective inspector in London. If you like Christie (which i do), you'll love Marsh. She was a theatre lover and you see the theatre pop up in many of her novels. for a list, you an have a look at her bibliograpy
HERE.