After Dark.

If it wasn't British, this would be in the Forgotten Horrors book. Hugh (Inspector Holt in HUMAN MONSTER) has some valuable jewels stolen. They're hidden in the back of an old clock in an antique shop. When the thieves return for them, the clock has been sold! They trace it to a creepy country estate. When Hugh and the niece of one of the crooks also show up, things get hairy.