Some farmers, whose barns are used regularly, seem to have supplies of these. Most do not. Hay bales are an alternative but tend to collapse slowly over the evening. As with barns, village halls vary from the delightful to the grim. They are normally big enough for most dances and come equipped with tables, chairs, electricity, kitchens, walls and toilets.
Prices vary from venue to venue without any clear reason.
It is worth shopping around. These venues are ideal for events like weddings and other celebrations where the dance is just part of the celebration. From the point of view of dancing, space is often an issue. The dance floor in a typical hotel or restaurant is big enough for only one or two sets of dancers. You should discuss your needs with the management.