The floor plan doesn't show the entrance door to the flat but I do think there is scope to increase the value and increase the feeling of space at the same time. And you get another usable room, like a study or spare room.
Move the kitchen to the wall behind the bathroom (should be possible because the water and drainage are already there) and create an L-shaped kitchen in that corner. This will be a larger and more sociable kitchen area than the existing one which seems cramped and stuck round the corner so not a very sociable space.
Because the floor area there is wider than the existing kitchen you might have space for a kitchen island or table and chairs. Depending on where the entrance to the flat is, that could also create a sort of walkway, past the kitchen corner on your right, into the main living area which opens up in front of you.
In the old kitchen area build a partition wall straight across and put a door in. This gives you another room accessible off the living area, with an existing window. The living area still has 2 windows which seems in proportion to the room and you have gained a study / home office / guest room.
I think that could be fab and not difficult or that expensive.