Provided the campervan you have rented has built-in toilet facilities and fresh water/grey water tanks on board you are allowed to 'freedom camp' in designated sites. Please obey local signage and regulations, and ask at local information centres [look for blue i-SITE signs or visitor information signs in each town] for suitable places to stay. Please do be aware that you may be fined for 'freedom camping' in non-designated areas.
To fully charge your campervan's auxiliary [house] battery you will need to plug the vehicle into 240V mains power regularly. We recommend you stay in holidays parks to charge the battery at a minimum every second night.
We recommend downloading the thl Roadtrip app for android or iPhone - you'll get up to date information on where to stay, places of interest on the road, as well as helpful locations such as public bathrooms, dump stations & supermarkets.