Hello zinm, and welcome to Flyertalk.

Personally, I'd really struggle to recommend any escorted tours to Paris - it's an easy journey and an easy city to get around.

As far as booking goes, I'd suggest a quick look at our Eurostar FAQ. It won't be easy to get cheap tickets at short notice, though.

If your French is up to it, you could check www.kelbillet.com or www.trocdestrains.com for resold tickets - caveat emptor, though, it's not strictly permitted in T&Cs (not that I've ever had a problem).

You can also fly to Paris, but the city-to-city journey time is usually greater than taking the train.