Which side of your house would it face? If it is South it is a common problem for it to be too cold in winter and too hot in summer. Underfloor heating is great in garden rooms I'm not sure about orangeries. When we built our kitchen extension we had underfloor heating with a gas boiler and it was really warm in winter. It was exceptionally well insulated though.

For this project, we installed a virtually frameless up-and-over roof light, a virtually frameless glass box roof light and Cortizo bi-fold doors. These elements can transform a space by flooding it with natural light, creating an illusion of openness and seamless integration between indoor and outdoor environments. The virtually frameless design of the roof lights ensures an unobstructed view of the sky, enhancing the area beneath's aesthetic appeal and ambience. It can make the space appear larger and more inviting, blurring the lines between the built environment and the natural landscape outside. Cortizo bi-fold doors complement this effect by offering flexibility to the space, allowing for a complete outdoor opening. How beautiful is this project? Get in touch if you have a similar project in mind.

Your existing layout has great potential, and your ideas for extensions make a lot of sense! A double-storey extension out the back could give you the spacious open-plan kitchen, dining, and living area you want, while an extension above the garage could create space for that fourth bedroom and second bathroom. For downstairs, you could use part of the garage or extend slightly to create a separate utility room. Knocking through the kitchen, dining, and lounge into one space would make it feel much more open, with big doors leading to the garden. Keeping a separate living room (maybe using the current lounge or dining space) would be a great way to maintain a cozy retreat. Upstairs, adding an en-suite to the new main bedroom over the garage could give you a fantastic master suite, while a double-storey rear extension could allow for four well-sized bedrooms.

https://www.loverenovate.co.uk/advice/hip-to-gable-loft-conversion/