I recently went on a road trip with my fiance in my mini. From Winnipeg Canada to Montreal, then NY, then Chicago, then Minneapolis, then back to Winnipeg. All told it was a 2 week trip covering 6000 km or so.
I realize that was of no help to you seeing as your in London but I figured I'd share anyway.
Only advice is make sure you pack lightly. By the time the two of us got back with the shopping we had done plus our luggage it was starting to get tricky seeing out the back window.