My bungalow was built in 1954 and the loft space converted in the 1980s, one large oblong room with a small en-suite - bath with shower hose as it is tucked in under the eaves.
The bedroom had no wardrobes but I was able to add one together with loads of shelves for storage in the nooks and crannies around the edges. It’s a large room but not the master bedroom due mainly to its narrowish oblong shape.
It has a velux window and I replaced it a couple of years ago with one that opens and closes using a remote control which I keep downstairs - it closes automatically when it rains! I use that on hot days to get fresh air flowing through my house and reduce the heat upstairs. It does get hot in that room if the window is not open and the blind closed but my visitors say it is not unbearable.
The initial survey pointed out the lack of insulation around the four walls although there is some in the roof. I paid for insulation to be added as soon as I moved in to reduce heat loss.
I do have an issue with sound insulation though as when anyone walks around upstairs, I can hear everything in my bedroom below so do ask visitors to be aware and tiptoe around! It’s not used that often, only by family when they visit, I also have another bedroom downstairs as well as my room.
If your plan is for the dormer to be used all the time, I would go back for a second visit and get someone else to walk around upstairs! Also be aware of the stairs, mine are slightly narrower than regular stairs but are not steep like some attic stairs as the original bungalow had a high roof and a decent hallway.