Some suggestions:
Aunt Dimity and the Duke / Nancy AthertonModel Undercover: London / Carina Axelsson
Double Crossed ; A Spies and Thieves Story / Ally Carter
Fifteen Days Without a Head / Dave Cousins
The London Eye mystery / Siobhan Dowd
Extremely Loud and Incredibly Close / Jonathon Safran Foer
The Curious incident of the Dog in the Night-time / Mark Haddon
Ride a Dark Horse / Lynn Hall
Mariner’s Compass / Earline Fowler
L is For Lawless / Sue Grafton
The Adventure of the Blue Carbuncle / Sherlock Holmes
The Secrets of Vesuvius / Caroline Lawrence
The Spellman Files / Lisa Lutz
Gem Stone / Dale Mayer
Rumpole and the Age for Retirement / John Mortimer
The Purloined Letter / Edgar Allan Poe
Gaudy Night / Dorothy Sayers
Ladies #1 Detective Agency / Alexander McCall Smith
Lost Book of the Grail: Or, a Visitor's Guide to Barchester Cathedral / Charlie Lovett
The Shadow of the Wind / Carlos Ruiz Zafon