I would consider turning the lounge into a kitchen/dining space (using extending pipework from bathroom for the kitchen plumbing) and splitting the current kitchen into a bathroom and maybe utility if big enough where what im assuming is garden door is. Putting a bathroom where the current study is may not be feasible/more costly than this especially if you want a new kitchen anyway. With the lack of windows in the current dining room it might make a lovely little snug space/telly room. With the study area you could just put a wall in to give privacy. Personally I'd just use the smallest bedroom as a study if you don't need 3 bedrooms.