Train travel between Paris and London

SalB

The initial impulse is to say the train. There are, however, some very low budget airlines operating in Europe and if you can get some of their special rates, flying is much cheaper than the train.

You do have to factor in the cost of getting to the airport and from the airport in the UK to central London. The low-budget airlines fly into and out of secondary airports that are often quite far from the central city. That said, you should check both train and air fares. Here's the train web site. http://www.sncf.com/

Here is one web site with budget air fares. http://www.harefares.com/

There are several carriers like Ryanair and I haven't dealt with them but suspect you can do a web search for budget European airlines.

For speed, the train probably is better since when flying, you have to get to the airport, go through security, fly, get your luggage, get from the airport into the center of town; whereas, if you take the train you go from center city to center city and don't have to deal with the security lines and waiting. The convenience might outweigh the price here.

Good luck.