If you hold 'Market Trader' specific insurance your answer will automatically be yes.
If you hold insurance for your business based at a physical premesis has this policy been extended to cover you while trading at and selling your products from markets/craft fairs etc? The important question in this instance is to ask yourself is 'Have you informed your insurance provider that you intend to trade at markets/craft fairs etc and does the cover provided include this additioinal activity?'
Evidence of this extension/cover should usually be included on your policy (or provided via a supporting letter/email from your insurance company to confirm that the insurance is extended to provde cover while trading at markets/craft fairs etc) Each insurance company presents their policies in different formats - If in doubt please contact your insurer for guidance.