Hi Littlemermaid
we have not tried it before, but we are going to try in April. It is detailed on the website and I phoned Eurostar to check and its all fine.
We figure it will save on parking costs and we will prob get someone to drop us at station and get a cab back. We are in Ramsgate so train journey is about 45 mins - so about as long as a car trip for us. I think that we will prob be there really early as I am pathologically scared of missing trains!!