I have put my focus on the layout with using the existing location of sink, with door ,window and boiler at the same location, I have created three option by ONLY moving the wall and work on different layout according to your requirement
By This:-
Low cost of construction.(no demolition of wall,door and windows location)
Less rerouting of the plumbing pipes

scale1:100
All dimension are in cm(i have attacted DWG file for dimension)