Information on short term accommodation is available from your local "Office du Tourisme"
You can also contact:
Maison de la France (French Government Tourist Office)
178, Piccadilly
London W1V
tel 0207 370 7744
You will find long term rented accommodation advertised in local newspapers or Paris dailies such as "Le Figaro", "De Particulier à Particulier" lists properties for sale or rent. Estate Agents (Agents Immobiliers) also provide accommodation to rent or buy. Look in "Les pages jaunes" directory for their addresses.