Approximate driving times using the autoroutes:
Arriving in St Malo - three to four hours drive
Arriving in Le Havre - five to six hours drive
Arriving in Calais - eight to nine hours drive
Flying to France from the UK
Arriving in La Rochelle - approximately one hours drive (Ryan Air or flybe)
Arriving in Nantes or Poitiers - approximately 1½/2 hours drive (British Airways/Air France/Ryan Air or flybe)
Car hire is available from La Rochelle Airport, and can be booked with your flight. If you go through www.auto-europe.co.uk you can get a 20% discount through the Hertz rental at La Rochelle and you get the excess refund option very cheaply too.