We arrive in London on Sun., Aug 4 and need to be in Harwich Mon., Aug 5 and on board the Celebrity by 5:00 p.m. Should we take the train on Sunday in order to avoid crowds? Anything to do in Harwich Sun. afternoon? Do we have to change trains to get to Harwich? Is that a problem with luggage? We are staying in Edinburgh after the cruise. Would you advise the train from Harwich to Edinburgh and then the train back from Edinburgh to Heathrow?