First, there is nothing like a Series/Defender and as of Jan. 2016 there is not even a current production Defender. These vehicles were designed to be easily modifiable into just about any configuration you could want with basic tools. They are boxes on wheels that have bolt on body panels. The tinker toys of the automotive world. Probably the closest you might find is a truck cab on a bare frame that you could build anything you want to put on the frame behind the cab.
You have not defined your needs well enough for a good reply. What do you mean by overland/off-road? Day trips, weekend and maybe up to a week camping trip? Or perhaps longer trips of a month or more? How many people? Do you want to camp inside the vehicle, outside the vehicle, or a hybrid style where part of your camp is inside and part outside the vehicle? Primitive camping or established campground camping? Primitive unmaintained trails or maintained forest service dirt roads? Daily driver or reserved for overland/camping excursions? The more you can define what the vehicle needs to do the easier it will be to have a set of vehicle parameters to look for. If you are camping outside your vehicle mostly all you need is seats for everyone, a big cargo area with lots of lash points, and suspension & ground clearance to handle the kinds of roads you intend to travel.
Define how many people, where you want to go and for how long, how you want to camp including expected campground facilities and if the vehicle needs to be your daily driver and you can narrow down the possibilities to make a much easier choice.
Can you further describe your needs?
