Depends on the house. An extension with bi fold doors and lantern to the flat roof, appears the way forward. For many houses this is the correct decision, providing a large light filled room.
But a conservatory gives the ability to sit in the garden. To hear the rain. A room not filled with light but to sit in the light. Modern glass roofs and windows are so different to the early conservatories. We use ours 12 months a year. It can also be used to bring heat back into a house.
A conservatory, even to modern standards, is so much cheaper than an extension. So small extension or large conservatory? Large conservatory every time.
Q