The average conservatory cost begins in the region of £4,000 to £5,000. This will be for a reasonably small and basic conservatory. The cost of a conservatory can be as much as £40,000 to £50,000. This will be a large conservatory, fully fitted with all building work included. As this is a wide spread it is a good idea to know your style and size in order to get an average conservatory cost.