I think two separate doors. But you could consider bifold. Have you had an opinion on the cost of adding the plumbing? And an opinion from Council on the feasibility?

What are you wanting to store? Is it still shed type stuff? As space is tight and if you have opportunity to put up a cheap freestanding shed (for storage) it might be better to accommodate a better 1.6 x 3.1 .bathroom right across the back of the shed and not take so much space up and give you more like a 4.5m x 3.1 space to have a den/retreat that is more flexible for purpose - also storage accessed through a nicely fitted out space could be less than practical

Given shed exists where is your water line and sewerage lines This may impact which side you put the bathroom on. Next what is being stored. If lawnmower etc then suggest external access only due to fumes. Otherwise can they share an internal door?

As others have said. What are you storing? I would cut into shed side and add a external door to access storage area. With having two hinged doors in side the studio area, you are reducing useful space. I would close up the internal door to store area, and add a sliding door to bathroom area. This will then create more wall space for kitchenette, or tv, wall unit etc etc.

Layout with one internal door

Meant to post this yesterday. two ideas, the store would be better elsewhere to allow more space but even an external double door to give easy access would works better but depends on what you are storing A coffee table that can be pulled up to dining height and moved when the night and day lounge is extended.

kitchenette backing onto the bathroom for access to plumbing

Thanks so much everyone for the really helpful responses. In terms of what we are storing - will be things like Christmas decorations, camping gear etc. All ‘messy’ shed stuff will be stored in another location.

We’ve had some quotes for the plumbing and spoken to council. We need council permission for change of use.

Layout with one internal door how high is the ceiling?

Going by the external door it's not a tall ceiling and would suggest painted exposed rafters at least in the living space.