The prices vary depending on what pass you have. Some passes only support one country, and others support up to 22 countries. The prices range from $49 to $509.
You cannot travel all the way from London to Paris by ferry. If you are in Central London, the easiest and most convenient way is to travel by Eurostar from St Pancras International Station to Gare...
I would check any regular travel site. I personally use Orbitz most of the time. Sometimes you can find a cheaper fare when you go to the airport site and search between the many airlines they offer....
Fares vary tremendously depending on the time of day you travel, how much in advance you book your ticket and whether you book for a specific train. The cheapest option is to book a single (or two if...