You need to check the hire contract for your contractual rights.
The company will be in breach of the contract if they fail to hold the fair and to provide an exhibition, or they may be obliged to provide a full refund. Under the wording of the hire contract the company may be entitled to hold the fair at an alternative equivalent venue.
Records at Companies House will show if the company is still in existence, or if it is in process of being wound-up (in ‘liquidation’ or ‘administration’). If the company is in administration or liquidation you will need to contact the administrator or liquidator promptly to make them aware of your claim on the assets of the company.
Your claim will rank behind that of any secured creditors and preferred creditors, such as HM Revenues and Customs, and employees.