Hi @Wuffles,
Thank you for your question and welcome to the Bunnings Workshop community, it is fantastic to have you with us.
Did you mean to upload an inspiration image with your question? If so, please let me know if you need a hand uploading pictures, I'm happy to help.
Unfortunately, it would be extremely difficult to give even a rough estimate due to the highly variable nature of the construction market. You would need to consider the cost of materials including waterproofing, tiles and tile accessories, lighting and electrical, toilet, shower, vanity, fixtures and fittings and other assorted bits and pieces. You would also need to take into account the cost of labour for electrical, plumbing and waterproofing as they are licensed industries that you will require assistance with.
I'd suggest contacting a bathroom renovation company for a quote. They can evaluate the room and using their understanding of the local market, offer a quote that is tailored to your specific circumstances and desires.
Let me know if you have any other questions.
Jacob
