I for Insurance
If a craftsperson is undertaking fairs /exhibitions etc then the minimum insurance they will need is public liability insurance. Supposing a customer were to trip over your draping table cloth and injure themselves - can you afford to pay out several thousand pounds in compensation? - and that's after the solicitor fees!!
For craftworkers, public liability insurance is reasonably inexpensive. I had a policy last year which cost me approximately £55 and this included product liability (ie if my product injured someone). An example of this perhaps would be if a post on a butterfly backed earring broke off in someone's ear.
Clearly I can't specifically recommend an insurer, however I can tell you who I have subsequently insured with (following an increase in premium by £20 in one year). I've never needed to claim, so I don't know how good they are on paying out - but... I'm insured with £5 million public liability (compared to £1 million last year) and have public and product liability within the policy.
I discovered AIR - www.a-n.co.uk for artists. It's a membership organisation which automatically provides insurance when becoming a member. Once you're a member, you can download the insurance documents. The cost for being a member of AIR for me.... which incidentally is a great online resource and sends out magazines (either online or paperbased depending on your membership choice) was £30 the year! You can also post details on the 'what's on' listings plus an image on the interface, as well as review and comments. It covers craft workers - but double check if it covers you for specifics relating to your craft. For example it doesn't cover 'hot works' when you're out exhibiting.
As I say, I can't recommend it - I can just say that it covers me for what I want and I found it extremely reasonable in price too..