We have a large kitchen/diner - it was originally a 3 room extension that we changed into 1 large kitchen/dinner. We have 3 areas of glass, the front door section is all glass (door in the middle with long glass panels either side, looks like bifold but its not..), we have the whole of the back wall as bifold and another small section of wall is glass top and bottom (top are windows). Difficult to explain.. We also have 3 roof velux windows (vaulted ceiling). It used to be FREEZING, but when we renovated we ensured much better insulation. Our builders wrapped it in a gold duvet thing. Again I can't explain but instead of having the ordinary type of insulation you can now get this stuff on rolls which looks like a duvet and they used that all over the house (and in the roof too). Despite our house being a 1450's period cottage it's probably the best insulated in the area. We also have water based underfloor heating - there's been many threads on the topic but it's now possible to buy an overlay system which can lay over an existing floor (rather than having to dig down which is costly). We have a stone floor (because of dogs and muddy paws) and its work beautifully underneath it. All of our glass units have integrated blinds within the glass. I found with bifolds (and I have a wall of glass in an upstairs bedroom) you will find it difficult to fit curtains if the doors are flush with the opening. So blinds generally are the only thing that will fit. Because most bifolds will be double or triple glazed there should be little requirement for curtains for warmth, purely for keeping out nosy neighbours etc.
The only thing I would say about electric UFH heating it is really expensive to run. We have it in an purpose built office that is in our garden (couldn't have water based as no water to the building). Our electric bill came in this month and was an extra £320 per quarter. The only real change in our living is this office. We have switched it off and bought a cheap heater and plug that in instead as we don't use the office every day and was heating an empty room for weeks/days we were not using it. When we turned it off, then turned it back on again it took 24 hours to come back up to temperature, which is why we have decided to turn it off completely. I find UFH only works in rooms which need it switched on all the time in a space you are living in. Because you can now buy an overlay system there's no real need to get electric if you can have the choice. Water is more expensive to install but much cheaper to run in the long run.