Can you post the current floor plan and tell us where both doors go to.
Is the plan to scale. At present the vanity obstructs the doorway. -

Hey Kate, this is the current floorplan and. The door next to the vanity is the one that goes outside and is not used very much, if at all. I can see how it seems to obstruct the door, but it isn't a main entry point. It's just there as a way to access the existing water tank. The main door to enter the bathroom is the one on the left of the room.

You could replace the under stair cupboard with a full height cupboard by flipping the laundry onto the stair side. You can then introduce a second door to really seperate laundry from bath if that is your design. This is a bit of work for a small gain in storage

Thanks Kate. Where would you position the freestanding bath? I have been thinking converting the area behind the existing shower into the laundry. What do you think?

the biggest challenge is access to the space under the stairs..what is the width and minimum height of the storage space and length of wall on either side of the storage door...and could that storage space be accessed from the kitchen side?

We're open to forgo the storage space under the stairs. The need for a bath and separate shower is more important than the need to access that storage area.

Is the laundry going to another space in house or into the hall cupboard to make space for bath?

Yes that's right. Thinking of combing the space that the dryer currently occupies with the cupboard and creating a European laundry which is accessible from the hallway. That makes the room more square but open to ideas of where the toilet, bath, vanity and shower could be placed from there.

Sorry missed bath. Try this

I put washer in the hall cupboard making it deeper to allow it to be behind a door. This cupboard is wide enough to store things for laundry. Hall cupboard went into bathroom entry. I moved door in but that’s optional. I used a back to wall corner bath as your room is not big enough for freestanding tub.
I moved toilet as that space is wider but if they are the same then you can keep in current location and you could have an open shower if you want.

Thanks Kate, unfortunately the access door needs to remain, so the toilet will need to be repositioned. I think the vanity will be ok where it is, it is still possible to walk through.

I have just seen the comment on the door needing to remain, so the shower could have a simple glass door that you can't see through, an indoor outdoor shower, with ceilings being 2.7 it could be perfect.

The following would give you a 3 way bathroom

Would this work?

My suggested shower would be similar to this using what you mentioned was a rarely used door

An alternative layout that leaves the toilet and vanity alone, but does require moving the 4 walls near the hallway to have enough depth and width for a washer/

Thank you everyone for all of your ideas!! You are all so creative!!! Something that is really important is the size of the laundry, relocating the door to the middle of the wall compared to the end means that we loose that extra space. I love the idea of the shower going where the toilet is! This is such a tricky space to work with! The other aspect is the size of the bath, ideally it should be at least 1500

Going off Jess's concept, would it work to move the vanity to where the shower is and have a 900m vanity, then move the shower to the toilet and move the toilet next to the bath?

I hope the following examples show how the passage entrance into the bathroom makes best use of the space. bath shown is 1500 x 800

The original entrance is a separate space, where as the suggested entrance uses the entrance space as part of the vanity space

Is this what you're thinking? I can't see why not.

It's an unusual space, with a million different ways to approach it. It's up to you what compromises you're happy with.

Yes that's what I was thinking. I thought we could put the vanity against that nib wall to make it focal feature as you walk into the room.

You have to compromise somewhere to add something as big as a bath. You may want to reduce vanity and add a tall cabinet to maximise storage and replace some of lost space from laundry.

I love your idea. The only problem is that there isn't any storage space in the laundry and also no sink