I would take the train to London from Harwich. It is about 1 hr and 19 minutes but it would be nice to see the countryside and the cows are the size of city buses don't be suprised. Also make sure to have a baked potato in England they are unreal. Don't miss these sites London eye, Westminster abby, Tower of London, and Buckinham palace changing of the guard.
Also for using a credit card there. Capitol one "Venture One" credit card
is the only card I use there because there is no annual fees and it does not charge a conversion fee. Which on other credt cards charge 3% - 5%. You must have excellent credit to get the Venture one card. For cash in British pounds use the ATM's they will give you the best rate. Stay away from the
money exchange places (which are everywhere) the rates they give our awful. Right now you would get 200 GBP for 300 US dollars that's not bad.
For hotels in the London area I use hotels.com | Hotel Bookings & Reservations Hotel Offers & Discounts Cheap Hotels Rates Lowest Hotel Rates Guaranteed!
I really like that you can pick the niegborhoods and bed and breakfasts are the way to go. Hyde park, Westminster, Victoria are nice areas.
National Rail Enquiries - Official source for UK train times and timetables
The train station is right across the street from the Cruise Terminal and will be very easy to find.
Use code HPQ for Harwich International trainstation and use code LST
for London Liverpool station. First class 13 euros and regular 8 euros.
You can only book 12 weeks ahead for you dates you may want to wait
a couple more weeks or by train tickets there.
Have a great trip and please give us a detailed report on how the trip went when you get back. Thanks Ed