Your home is lovely, my thoughts are if you are hesitating about the dado rails, maybe consider turning them into an elegant and timeless feature, by converting them to wainscoting? (I sense from your question that you are not a devotee of the Victorian style :-) I also agree with what the others have mentioned about changing the colours to something more neatural like a shade of grey that you like or a dusty blue, and leaving the lower half white. For a more updated look, you could look at updating the pendant lights to something a little more classic, (to your taste of course) and if budget permits, changing to carpets to perhaps a hardwood floor. All the best, I hope this helped. Ive attached a picture and link to an example. http://www.charmingzebra.com/2011/07/wainscoting-success-sort-of.html

lots of advice in response to your question on Google...i like to align with top of vanity at about 850 to 900mm above the floor but, if you need a towel and grab rail for safety of disabled and elderly there are specific recommendations but main criteria should be comfort of main users and size of your towels

We recommend a 4 bar heated towel rail, there are also new vertical towel rails for a more modern unique look. https://bathroomwarehouse.com.au/products/thermogroup-straight-round-vertical-single-bar-heated-towel-rail-matte-black?variant=37433864356006&currency=AUD&utm_medium=product_sync&utm_source=google&utm_content=sag_organic&utm_campaign=sag_organic&creative=509193521705&gclid=Cj0KCQjwh_eFBhDZARIsALHjIKeaxD7YRLQXJgYv0Cg9DOBle1hqwt3A-nEW8BqKDonMyS0lVzNDYJMaAkejEALw_wcB

First step would be outline what and why the railing and deck needs replacing , so that you ( or we ) don't repeat the mistakes . Like oklouise said , what is the front and rear deck made of ( sounds like they are concrete slabs , but just checking ) , what are the rails currently , do you know how solid the pillars are ( they look a different brick to the house , so may have been added later and/or have steel uprights in the middle , etc ) . The answers to those questions will give 'us' a base -- a concrete deck or two is harder to replace than wooden ones , same with steel poles imbedded in 2 metres of concrete etc . Just some general comments though -- what is the material between the 2 windows on the upstairs front ? And you say about not replacing the windows , but possibly changing the rear door ? Is that because of cost ? The brown frames will always date your house , but they are no where near as bad IMO as the yellow glass . Personally , that glass would be the very first thing I'd change ; 2nd thing would be doing charcoal on the gutters and garage doors ; THEN I'd update the decks and rails . Depending on what the fill panel between those 2 upstairs windows above the garage doors is made out of , maybe paint it off-white or charcoal -- add some interest in a subtle way . If you keep any part of the blue rails , paint them . Also look at some landscaping , a solid brick or maybe charcoal coloured concrete mailbox , charcoal stained fences -- but I still shiver at the yellow glass haha .