The Wicked Godmother (A House for the Season #3)

 
Young Harriet Metcalf has come from the countryside to Mayfair, and her assigned task is to get two teenage heiresses launched in the London ton. For the course of the season, they will be renting at 67 Clarges Street—where the quirky but resourceful servants are always ready to lend a helpful hand.
 
But Harriet soon finds herself being courted by a notorious rake, the Marquess of Huntingdon—much to the annoyance of the spoiled young sisters. The below-stairs staff may just have to step in to set things aright . . .
 
Originally published under the name Marion Chesney,