Venue ideas for volunteer events in rural areas?

I manage networking and training events for a large group of volunteers which I manage - 2500 people across a large part of the West of England.

When you are working in a largely rural area what do you think are the features of venues that are most important in getting a big crowd along?

Our rural area includes Somerset, Wiltshire, Gloucestershire and Dorset. Any suggestions for cheap or free venues (we have very little budget for events!) that would attract a crowd?