Smaller mishaps, such as rotting flowers or ripped suits, usually trigger a single payout for the cost.
But if the problem's so severe – say, your venue has flooded – that the wedding has to be rearranged, then your insurer may instead arrange an alternative wedding, so you won't actually be paid any redress, it'll just sort out the new Big Day.
Notice the emphasis on the words usually and may, as there's no one definitive rule; it can vary by insurer.
Don't forget on any claim there's an excess to pay. For example, say your wedding flowers are a write-off when they arrive: you might typically be entitled to £2,000 cover but have to pay a £25 excess, so only get £1,975 back.