One of the beauties of UK touring caravans is they are designed to able to be used off grid with no 230V being available. This is why you have diversity of energy sources for the fridge, water and space heaters. You may not be able to use the 230V ac appliances, but you do at least have the means to keep the fridge working, keep warm, heat water for washing, cook food, and boil water for hot drinks all by using the gas.
Other functions such as lighting and entertainment can be managed with 12V systems. It helps to have some form of of grid 12V charger, which can be achieved without a portable generator by using solar cells.
You do have to recognise you need to be aware of the limitations of each of these systems and exercise good energy management, Only turn items on when you need them, and also turning them off when you don't. Only using as little water as needed. You may need to plan a little further ahead when for example cooking, as caravan cookers do take longer than their domestic counter parts.
You may not be able to watch TV as long as normal becasue of the limited capacity of the caravans battery.