I'm in the very early stages of planning our trip and one of the biggest obstacles I'm facing is how to move 12 adults from place to place. We plan to start our tour in London, then to Paris, Germany and ending in Italy. I'd appreciate any suggestions and/or help on how to logistically move 12 adults around Europe.
I can't help you in UK, France, or Italy, but I do know Germany. There are discounts for 6 or more people. They require arrangements in advance, but, usually, they are not as good as the regional passes, Bayern-Ticket, et al, you can always get. For longer distances, the Sparpreis offers very good discounts with a little more off of the 2nd through 5th traveler.
Look for fares on the German Rail website