Is it possible and/or cost effective to pick up a car at Gatwick and drop it off in Harwich a few days later? We'll be arriving about 4 days before our cruise leaves from Harwich, and this would give us some mobility. Thanks.

Sure it's possible. Most major agencies don't charge extra for one-ways within the UK.

Of course if your itinerary includes London, fuggedaboudit.

This can be done, but please consider Gardy's question. If you will be spending those days in London, renting a car is a very bad idea. For driving around the countryside, renting a car is a good way to go.

As long as your rental car agency has an office where you want to drop the car off - usually no problem. On our last U.K. trip we picked a car up at the Glasgow airport and dropped it off at Gatwick - no problem.

Thanks for the replies. Yes, I knew that driving in London wasn't really a great choice; I did it once, when I picked up a rental car near Victoria Station on our way out of town, and discovered that London was nervewracking even for one brought up on the streets of New York City.
A lot of rental agencies on this side of the pond do charge extra for one-ways, which is why I asked.
We're not sure if we'll just be staying in London until we have to get to Harwich (I think there are direct trains), or if we'll simply get a car at Gatwick, and drop it off near/in Harwich before the cruise. So far I haven't seen any car rental firms with offices there, but I haven't done much looking either.
I really appreciate the advice.

<<< So far I haven't seen any car rental firms with offices there >>>

A quick google suggests that there are one or two

Ok, now that I've gotten some very good answers to my prior email, I have another question (naturally). We're now thinking of renting a car when we return from our cruise (we'd stay in London before the cruise). Apparently, the company I'd prefer to deal with has a rental agency in Ipswich, but not in Harwich. They don't seem that far apart, but I was wondering how we could get from Harwich (where our trip ends) to Ipswich? Any knowledge of public transportation there? Thanks again.

I'd check to see if the rental agency also has a location in Colchester. You can take the train from Harwich to Colchester or Ipswich, or you could take a taxi to Colchester (about 16 miles)

Thanks for the advice. I'll check out Colchester, too. I didn't realize trains ran on the route (which is why I asked, I guess). I appreciate the advice.