Train London to Champagne

Sorry what is question? Are you staying in Paris for fora few days,,,do you mean simply to transit?

Where in Champagne? Reims? The Eurostar from London ends in the Paris Nord station. The trains to Champagne-Ardenne and Reims leave from Paris Est station. The stations are about 700 meters apart. You could take a taxi if you have a lot of luggage, but you may have a long wait in line for one.

As Chani said, there are no direct trains from London to the Champagne area. The Eurostar arrives at Gare du Nord, and trains to Champagne leave from Gare de l'Est, but the two stations are very close together and you can make the trip on foot unless you have a huge amount of luggage or mobility problems. You can get significant discounts on train fares by booking from London to Paris around six months in advance at www.eurostar.com, and Paris to Rheims or Epernay about three months in advance at www.capitainetrain.com