Normandy to London

The service is limited but you could fly to London Southend airport from Caen, France or Rennes, France if you don't want to go back to Paris to catch the Eurostar.

or you can take a ferry from Caen or Cherbourg to Portsmouth.

Pretty much fly, float or ride the rails.

If you're not interested in visiting anyplace in southern England (nearer to the channel than London), then returning to Paris is probably your best bet -- either to take the Eurostar or to fly.

If you choose to "float" instead, be aware that not every ferry port has a boat crossing every day of the week. They tend to rotate -- and for some periods of time the schedule is cut back as boats are taken out of service for maintenance. Then too, a ferry can be canceled on short notice due to a labor strike. That happened to us and we had to drive like crazy to a different channel port to catch the only available boat to England that day.

Keep in mind that this June marks the 75th anniversary of D-day. If you are planning on going anytime near then, be aware that most lodging has been booked for years. That being said, although there will be huge crowds, it is also a huge area. You may be blocked from certain areas right around the anniversary by visiting heads of state, but the D-day landing beaches are 45 miles as the crow flies. So there will always be somewhere to go and some place to see.

I've had two of five channel ferries canceled on me, so be cautious about depending on that mode of transportation if you have a tight schedule.