Loft Conversion - weighing up our options

Our flat is located on the second floor of a three-storey building in a conservation area. On the second floor are three bedrooms, a small living-room, a kitchen, a bathroom and two large cupboards in the corridor. We have a loft on the third floor which we are looking to renovate. At the moment, we can only access it with a ladder and have only used it as storage space. It is an old and dusty room with no windows.

We are still discussing what we'll do. We have narrowed it down to three main options.

Option 1: Master bedroom + small bathroom
Option 2: Large office + home cinema area
Option 3: Open-plan kitchen + living-room

With Option 1, we will have to comply with fire regulations. Option 2 is probably the easiest one and is ideal for people like us who work from home and can have their own space during the day. Option 3 is the most ambitious but would allow us to turn the living room and kitchen downstairs into an ensuite bedroom.