Save the pink bathroom! The original floor and the pink bath are beautiful! And obviously appropriate to the era of your house. http://savethepinkbathrooms.com/ To give you a more spacious feel, have the door replaced with a cavity sliding door - it gives you an amazing amount of extra space, we did it in our bathroom I would replace the vanity, which is obviously not original, with a custom laminate vanity with cupboards underneath in pink (top) and grey (cupboard doors/sides) or even a boomerang pattern for the top (http://retrospaces.com.au/retro/images/laminates/Renovation/FirstLadyPink.jpg) have a skilled tiler repair any areas that need repairing and have the tiles professionally cleaned and re-grouted and re-do all of the silicone, Then replace all the tapwear with new chrome taps but in an appropriate style (like these for example http://www.caroma.com.au/bathrooms/taps/retro/retro-wall-top-assemblies) and a new glass shower screen. A really fresh coat of white paint (use the bathroom product), better lighting - put a light in above the mirror (http://www.ikea.com/au/en/catalog/products/00255303/) and a fan/heater/light in front of the vanity exactly above where you'll stand when you get out of the shower. If the mirror isn't in good shape (or it may be mirror doors on a cabinet? I can't tell) then think about replacing the mirror too. You'll save a heap of money over completely re-doing the bathroom and importantly you'll be in keeping with (and preserving) the midcentury design of your home.

thanks to everyone for your helpful comments! I was going to have to pay around $190 for 6 more, but will order them from Beaumont who have a 25% sale on at the moment. I agree that I need to just live with the cost and finish the job properly, but your shortcut suggestions were all really interesting and much appreciated. And archimondo, I'd say it's like having a kangaroo loose in the top paddock.

If you've got great project management skills, design skills and an understanding of the building process for wet areas then go for it. If not I'd recommend hiring professionals, remembering you are not just paying for the work they are doing but also their training, experience and knowledge whether that be in design or building. Some of the bathroom product supply companies offer a design service (with varying level of design skills) and some builders can give you design advice (sometimes great, sometimes not). Alternatively, there are plenty of Houzzers who are happy to offer design advice and suggestions if you wanted to throw up your floor plans and a wish list. Once you've got your design in place I'd either hire a builder to manage the project for you or do some serious research into wet areas and engage trades as required, depending on your skill level; remembering some work like electrical and plumbing must be completed by a qualified trade. There are also a number of specific Australian Standards that need to be adhered to in wet areas for yours and others safety, now and in the future.

Thanks for the measurements, there were a few missing that would have made it easier to be more precise, But I'am making suggestions on what I think might fit within the existing floor plan which you are trying to do. the only small extension is to fit the laundry into a shared family bathroom. As there is already a shower and toilet in the current laundry I think it would be wrong to move them as they are close to your new alfresco area for the family to have easy access when you have your get togethers. To try and keep the girls bedrooms a good size and together with the other two bedrooms I suggest working with the fireplace and making the current Bathroom and ensuite but with the ability to share the toilet with the girls during the night. I have added my beloved barn doors to close off the kitchen from the bedrooms and also to be able to leave open during the day for extra light., the planned deck with roof over will make the dining/study/kitchen darker so you might need to consider a sky light. Anyway just a few different ideas trying to work with and around special features cheers