This will depend on the park the static caravan is sited on and the build standard of the caravan. Most holiday parks have holiday licences so there is a limit to the time you can stay in the caravan which could be up to 11 months. Most caravans are built to EN1647 standard which caters for seasonal holiday use only, but it’s recommended you look for a caravan that is BS3632 if you plan on holidaying for large periods in the winter. Note if you do intend to spend most of the year using your holiday home Leisuredays can offer cover for extended personal possessions.
If you intend to use your unit as your main residence your park will need a residential licence and you will have to pay Council Tax.