You are liable for taking out any insurance that may be required for you or your event.
You will need to ensure that you have the necessary first aid if it is required for your event. St John Ambulance and the Red Cross may be able to provide first aiders for free.
Food and Alcohol
You can find out about the regulations around providing and serving food at an event at www.food.gov.uk.
If you have hired a venue for your event and wish to sell alcohol you will need to enquire if the venue has a license to sell alcohol. If the venue does not have its own license, you will be responsible for attaining a license by applying to your local authority.
If you are providing public entertainment and your venue does not have a public entertainment license then you will be responsible for attaining a license by applying to your local authority.