There are many different options here:
P&O Ferries run up to 25 crossings a day from Dover to Calais. The crossings take approximately 2 hours. They also operate an overnight service from Hull to Zeebrugge which is convenient for travellers from the north of England or Scotland.
MyFerryLink (www.myferrylink.com) is a new ferry company operating two state-of-the-art ferries to France on the Dover Calais route. With 16 crossings a day there’s bound to be one that suits your schedule. For a great car ferry deal book your ticket online.
Brittany Ferries (www.brittanyferries.com) run crossings from Dover to Calais and Portsmouth to Caen, Cherbourg and St Malo. They also run crossings from Poole to Cherbourg and Plymouth to Roscoff. For those travelling from Ireland, Brittany Ferries also operates a service from Cork to Roscoff.
DFDS Seaways (www.dfdsseaways.co.uk) is the World's leading ferry operator with ferries to France (Dover to Calais & Dover to Dunkirk, Newhaven to Dieppe and Portsmouth Le Havre), ferries to Holland (Newcastle to Amsterdam), and ferries to Denmark (Harwich to Esbjerg).
Condor Ferries (www.condorferries.co.uk) operates Catamaran services from Poole and Weymouth to St Malo via the Channel Islands. Also a weekly conventional ferry service Portsmouth-Cherbourg, late May to early September, popular with caravanners.
Driving times to Razay are (approximate):
Calais - 5 ½ - 6 hrs
Le Havre - 4 - 5 hrs
Caen - 3 ½ - 4 hrs
Cherbourg - 4 - 5 hrs
St Malo - 4 hrs
Roscoff - 5 - 5 ½ hrs
Most car hire companies advertise through car hire comparison sites. They do not normally charge commission and regularly offer good deals. Most car hire comparison sites give you an instant overview of options from numerous companies.