Your floorplan is really logical which is a bonus. It depends on your budget. I would look at knocking down walls between the kitchen, lounge and dining room first to see if that would give you enough space without building an extension. Do you need more bedrooms? If you don't a single storey extension would look fantastic with rooflights or even a glass roof and give you a lot more living space. Does your garden face south?

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.

Unfortunately the house faces north