looks like you already have some type of counter, separating dining room from entry to bath and bedroom? if yes, I would suggest placing open shelving between entry and dining. you can decorate upper part of shelves with old books and art frames and at the bottom part I would place leather or wooden boxes too keep everything in it. this way see-through shelving will provide separation and would not block light in the study. I would suggest placing desk against the counter. in this case when you work you are not confined in small space and still see whats behind the window.
to give you more privacy you can decorate your counter with glass lanterns or glass objects, so they do not block light which is so essential for study.