My wife and I disembark in Dover. Would like to spend the day there and then take a late afternoon train to London. Questions. Is there anywhere to "check" our baggage? Is the train station the ONLY place to check our baggage?
Id call one of the many little B&Bs near the train station and explain your dilemma. I would bet for a small fee they would be happy to watch your bags for the day. Some of them even give private tours and such. In that case you could lock your bags in their mini van or other such vehicle.
Dover castle is a must see and the double decker bus tour of the city is quite interesting.
The other choice might be to just rent a car for the day and lock your bags in the boot.
Or if you have lunch in one of the larger hotels on the water, their porters (if well tipped) will undoubtedly watch your things for the required amount of time.