We would recommend a second leisure battery for when you go off hook-up. Adding a second battery will give you access to more amenities, and you won’t have to worry so much about other devices draining too much power. A motorhome-friendly sat nav or mobile app is also essential, in our opinion.
Other accessories and key things to take in a motorhome we would recommend include: a reversing camera, a dashcam, solar panels and a bicycle rack — but of course you would only need one if you plan on doing a lot of cycling.