[Closed] Public Liability Insurance advice...please (yawn)

The wife is booked into a few craft shows to sell greetings cards.

They'll be a small table with a few chairs on a very small plot - both organisers have recommended she takes out PLA.
CMTIA (Combined Market Traders Insurance Association) only offer it for an annual fee. Does anyone know if it can be done on a event by event basis as we don't know yet when the next ones will be, or even if it's worth doing this way or pay a one-off annual fee (or even at all!)

As she doesn't employ anyone or use machinery (in the events anyway), she's unlikely to have anything on her stall (aside form a table collapsing) that will cause damage – though there's always some muppet that might make a big deal if something did go wrong!

Could someone advise if they have any PLA pretty please.....cheers