Are these dormers just for a window or for living space with floor and what size and height do you want? How deep will the dormers be? Do the upstairs rooms have sloped walls from the roof and if so how high on the wall do the start? Do these rooms have flat ceilings and what height? How far from the peak of the house to the ceiling? What is the pitch of your roof? What size rafters do you have now? How far horizontally from the rooms inside walls to the gutter? What kind of roof covering? What kind of siding? What size of windows? Is this a flat top dormer or a peaked one? What slope/pitch do you want on your dormers? What size is this cottage? What is the present roof design? How much insulation will you put in?
That is enough questions for now. Like the others said, not a typical project for a diyer unless you know framing and roofing, etc cause it is very involved. If you have the experience, you won't find any plans to fit your cottage anyway since sizes of everything varies so much. You could size everything and have an architect draw it up(or find a contractor to draw it up). Even then you may have some angles that don't come out perfect. But as "the contractor" said (but probably said for the experienced), is that an experienced framer can and would cut and make his rafters, etc to fit the size of dormer he/she is putting in after all the experienced don't need plans for everything. This won't be a cheap project either. You will also have open holes in your roof for a while which may get uncomfortable in a place like canada.(I assume canada since the .ca after your email address stands for canada.)
Last but not least, go to your local library, bookstore, and home cheapo and you will find plenty of books and magazines with pictures and plans that have dormers which you may be able to adapt from.
For "the contractor" guy, help on this board is now and in the future always appreciated but remember you are probably responding to novice diyer's and should answer accordingly.