Welcome to the Bunnings Workshop community. Thank you so much for joining us and sharing your question about how to measure and order a frameless shower screen.
When measuring the space for a new shower door, I suggest placing your tape at the edge of the wall and measuring to the other side. It's important to measure the width at both the top and bottom end of the door as it might not be square. The same rule applies to your other shower assembly. I suggest visiting your local store and going to the Special Orders Desk. Ask them for Rick McLean's Custom Door Brochure. In the brochure, it will ask you for measurements and details about what kind of door you're after. This will then get sent to Rick McLean's to get quoted and then the Special Orders Desk will get back to you once the quote returns to the store.
The other frameless door is the D'LUCCI 10 x 2000 x 865mm Frameless Glass Shower Panel Door Kit, but this comes only in a fixed size. To make this work, you will have to modify the opening of your shower. It's done by adding a timber piece that is covered in tiles or a cement column is built. A standard D'lucci plain panel can be purchased at the store for your two-sided shower.
Unfortunately, there is only a bathroom renovation service available at this time. You will have to find an installer on Hipages or Airtasker. Are you renovating the entire area or are you just changing the shower doors? Will you be re-tiling or painting the tiles? If you are, have you considered painting the shower frames? It sounds like a fantastic project. Any updates you can provide would be much appreciated.