Pardon just read this and as a Londoner and having cruised a few times from Dover, which is less then an hour from us, I thought I would jump in.
Train line is the official train website for all the UK and Southeastern the local operator for Kent and suburban train services from London to the south east, fates should be the same, note high speed trains run from St Pancrus to the north of the city, and normal dumber an services from Victoria and charring cross ( Also Waterloo east). Now high speed are great but more expensive. Travelling before 9.30 on a weekday will be expensive. Single Trip tickets are more expensive to returns.
Also buying in advance will be cheaper than say a week or so before.
Please do not use London Brudge station it's under reconstruction and many SE services do not stop there this year.
You have to get a taxi from Dover priory to the ship. It's short and cheap, and a few taxis outside the station.
I had a trip report from the last cruise to call at Dover in 2015, with travel information, photos, navigators, videos, and embarkation information.
torussiawithmickeybars.blogspot.co.uk
torussiawithmickeybars.blogspot.co.uk
Now Dover has a small terminal embarkation and check in will be later than port Canaveral, do not show up at the port entrance before 10.30, then it still maybe slow, if you arrive early thry will tell you to go away.
Weather in the UK is changeable, so you can predict if it will be raining, sunny etc. We have been lucky sunny departures on our Dover cruises, the pools were used, the slides were fully used, but a bit cool in the wind, the pools are heated but you need a towel as soon as you are out.
PS We are doing your cruise in reverse in July, we have booked private tours and guides in all the ports, as they are better value than
DCL, you see more, do more, less tourist stops with high pressure sales, we all get a window seat and personal service, not looking st the inside if s coach with 55 people and st tour times we choose.
Have a great cruise.