The simplest way for how to turn a conservatory into a room is to insulate the roof. After all, most of the heat gain and heat loss in a conservatory is due to a glass ceiling.
There are great insulation options on the market and the one we recommend is tailor made for turning a conservatory into a room. The insulation will make sure you will no longer lose heat during the winter months, and gain heat during the summer months.
The technology used for this insulation system was first developed by NASA. The space center used multi layer foil insulation sheets for the Apollo space missions, trying to protect spaceships against extreme temperatures. So, if is good enough for NASA, it should be good enough for you.