I've been watching a tv series called Room to Improve, with an Irish architect. Unfortunately it finished today. Anyway, an architect is called in to remodel a house and extend if necessary. Sometimes this involves knocking down down existing extensions. He tends to create an open plan living, kitchen and dining space but not always. It depends upon his clients needs and wants.
If you are happy where you live, why not think about exactly what you need and would like and then get in touch with an architect or two and see what they come up with. Many years ago, when we were doing up our wreck in London, we asked an architect friend for some advice, just related to our bathroom etc and he came up with a very simple solution which we wouldn't have thought of.
Years later we thought of extending our Suffolk cottage so that we could create a second bathroom, amongst other things. Another architect friend discussed what we wanted, and came up with a plan which converted our existing kitchen into a new hallway and shower room, linked to a new kitchen dining room with a utility room. It worked very well. We didn't build it because we moved to France but we gave the plans to the purchaser and he did. We have since seen it and it is excellent.
Don't forget the legal fees, estate agents' fees and stamp duty before deciding whether to move or not.