Fire escape from upper floor ( as this would be a type 3 space ) I can go out onto the roof over the office as that is single storey or from the landing via a new escape type window. Which means I don't need a kitchen door. Closing off the old side door entirely could be a workable idea having read through a few posts here. Putting a partition and door to form a small hallway outside the office is actually a neat idea and effectively completely separates a home based business from the living space as well as offering an 'air lock' to keep weather out.

Thank you all for your help so far! What colour do you think the bigger rug should be? I was looking at things like this https://www.houzz.co.uk/products/metro-rug-black-and-white-60x90-cm-prvw-vr~116921750 https://www.houzz.co.uk/products/jersey-8420-rug-stone-140x200-cm-prvw-vr~112201633 https://www.houzz.co.uk/products/copperfield-rug-60x90-cm-prvw-vr~116921735 but is it too much of the same colour for the room?

Excellent idea there by @Jonathan. You'd have to move the radiator (or perhaps change it to a column and place in the corner?) but it'd be a nicer placement of the bed, better paths around the room and way more storage. Personally, I'd go one less wardrobe and have the vanity table and chair parallel to the bed with a large wall mirror and overhead shelves If you want a simpler option, option 1 looks the best solution.

Re C: Sorry to throw another idea your way, but there is another way to set out the storage in C. Rather than have the cupboards/wardrobes opposite the bed, you could dedicate the space under the sloping roof to the cupboard/wardrobe. ie there would be a long row of storage running parallel to the bed. (I've had this in one of my houses). To look at the wardrobe doors look square. The pitched room is hidden behind. The advantage is that you can then have sliding doors on the wardrobe, and a long hanging rail. It's only a half height -- so not good for dresses, full length coats - but fine for shirts, skirts, suits etc. This leaves the wall opposite the bed (in orientation C) free for drawers (maybe two sets of drawers - if two people are using the room) and you can display photos/vases/ etc attractively on the surface of the drawers. Maybe put art work/photos above the drawers (which you can look at from the bed), or wall paper the entire wall. So - you get a long row of hanging space (behind neat sliding drawers), you can store stuff behind and below your hanging space (because the eaves go back further), you have plenty of space for proper drawers, and you look at an attractive wall when you walk into the room. (Disadvantage - not much full height hanging space - you could add some but not alot behind the door)