Costings

To start your process, you will need a good architect and maybe a structural engineer. If the cottage is a listed building, you may not be able to make any major alterations. Is there any similar properties in the area that have done similar. The problems I can see, as you say it has a low roof pitch, you are going to need a good head height, bearing in mind you will more than likely have to put in larger floor joist, which will reduce it even more, you may even need steel work fitted. Before you proceed I would suggest a visit to your local planning department and see what there opinion is, they could indicate wether you can or cant obtain planning. If it sounds positive, you will then need an architect, who should also know a structural engineer that can work with him. If you choose a good architect he should be able to design your conversion that would go through planning, and organise the building regs. As we dont know the size or spec of the conversion, we couldnt guess at a price. Your architect should be able to give you some indication.

where are you based ? as it will effect the cost of conversion

you would first have to get planning permission, this would require a architect to draw up a plan, if successfull you would then have to get building regs then you couldpost a job on this site to obtain several quotes from tradespeople in your location,regards Terry.

expect to pay around 2500 for drawings and structural calcs ,then extra costs for building control 500-750 varies between areas ,typicall dormer loft construction cost start from 15k upwards depending on size spec of works and finishes required