Welcome Gerben en Ilona.
As you have found out your Eriba does not have a large onboard tank and as such it will not have a hot water heater.
I fitted a large tank and electric water heater on a Familia 310Gt back in 2011. You fill the tank from the outside through something resembling a petrol filler cap. We use a cheap watering can and this is a lot more convenient than the small tanks you will have under the sinks The job is fairly straight forward if you are competent and organised at practical tasks. Fiamma do a suitable tank that is readily available and the TrumaTherme water heater is your best option for the price. If you start going gas/electric combination it will be expensive. Your taps are also going to be a significant cost as those in your van at present are not set up for hot and cold water.
Thule do a nice quick to deploy wind out roof awning, but I'm guessing this would be about Euro 1500 fitted. The Fiamma Caravanstore zip bag canopy is a nice quality option but fowls on the door and is annoying. You can get around this by gluing and screwing another awning track about 120mm above the existing gutter/awning track. The other option normally taken is the excellent Isabella Shadow canopy. This can be up and secure single handed in 5 minutes.

Best of luck in your modifications and please feel free to ask lots of questions.

Colin

Hi Gerben en Ilona and welcome to Eribafolk
Randa