UK to France options
Calais to Dover is the fastest sea route from the UK to France. It takes about an hour an a half, once you're on the ferry, to get across and there are dozens of ferries each day. There are 2 ferry operators, DFDS Seaways and P&O Ferries, and it is also possible to get Le Shuttle - the Eurotunnel train, which you get on in Folkestone and takes about 35 minutes to reach Calais.
Prices vary hugely and it's best to book in advance as you can grab a ferry crossing for as little as £20 each way. We've enjoyed many crossings on all three options and we particularly enjoy taking the DFDS Ferry and booking the Premium Lounge which is such a lovely, luxurious way to start a holiday!
Other options to consider are the DFDS Seaways route from Calais to Dunkirk which is a longer crossing (2 hours) but the port is much smaller and shouldn't add too much time, if any, to your journey. It's a great choice if you're heading to Belgium or the Netherlands.
Longer ferry routes to France are available on Brittany Ferries* from the south coast of England (Portsmouth, Plymouth and Poole) to a handful of French ports on the west coast (Le Havre, Caen, St Malo, Cherbourg and Roscoff).
One other route which we really like is the DFDS Seaways route from Newhaven to Dieppe. This ferry is often a real bargain price and these smaller ports are rarely crowded so it's easy to board and disembark.
One final thing to note is that not all crossings and all routes allow foot passengers so if you are going without a vehicle be sure which routes are suitable for you.