Best and most cost effective way to get from London (Heathrow) to dover to catch a cruise ship. We have traveled with Rick; but, we also enjoy cruising.
Fastest (1hr10min) would be a high-speed train from St Pancras International to Dover Priory. Or you could travel from Waterloo-East to Dover Priory in 1hr50min.
As already noted, the fastest option is the Southeastern Railway service from St. Pancras International, which is convenient because it's on the Piccadilly underground line from Heathrow. A cheap alternative is a National Express bus. Heathrow to Victoria Coach Station is around £6 and then Victoria to Dover from as little as £7, but it does take a total of at least 3 hours 35 minutes. Journey planner at www.nationalexpress.com
Oops! In my previous post I forget to suggest a route from Heathrow to either St Pancras International or Waterloo-East. Take the Tube (Piccadilly Line) directly from Heathrow to King's Cross/St Pancras. Take the Piccadilly Line to Piccadilly Circus and the Bakerloo Line from there to Waterloo.
Tim, the Southeastern services that run through Waterloo East all start at Charing Cross, which may be a bit easier to get to (Jubilee rather than Bakerloo). EDIT: well, I managed to garble that pretty well... Jubilee and Bakerloo both go to Waterloo, but it's a bit of a walk to Waterloo East. Charing Cross is on the Bakerloo (change from Piccadilly line at Piccadilly Circus).
Do please realise that Dover Priory station is a fair distance from the port. The previous port station has been closed for years. You'll probably want a taxi from the station to the boat.