Tile is still the best thing for a walk-in shower to be waterproof. Neither the cork or hardwood will be. Think about installing a radiant floor under the tile like Sharon recommended. I like the NuHeat Radiant floor system the best.

You have "wear through" which is when the finish is pierced and the wood is exposed to the elements. The dark areas are where dirk/water/mud have stained the floor. It is possible to get this out... but probably not all the way. A floor that has wear through needs to be sanded right down, stained (if you wish) and then refinished. Patching can occur...but it is almost always a waste of time because the "look" can be very different from the original sitting right next to it. I don't recommend it for your situation. The second photo shows the deep scratching. Ideally, you would have had your floors looked after BEFORE wear-through occurs. There are some "regular" scratches to the Left in photo 2. You can see it is visible...but no discolouration....THAT is where you draw the line. The darker "wear through" to the Right in photo 2 = too late = full sand and refinish. If you catch it BEFORE wear-through, you can do a "buff and coat". This is a light sanding with a few coats of high end finish over top. The buff and coat is roughly half the price (in Canada at least) as a full sand/refinish. For this reason it is important to catch the floors before you get to this level of scratching.. That being said, you now get to pick some stains (test patch, test patch, test patch). The first photo shows two different woods...you could ask to see if the lighter would could be matched to the darker wood (lots of testing to achieve this). It won't be pefect...but then again you wouldn't have used reclaimed building materials if you were after "perfect". The match can lessen the colour variation to a more manageable (design wise) level. As for "good for dogs" - natural colour of wood = best colour for scratches. A lower gloss (like a satin) can help. You can ask for the "best" finish with scratch resistance that comes in a can. You will pay a premium for it...but it could/should save you thousands of dollars over the long run. A highend, scratch resistant finish means you can get away with the cheaper buff and coats (every 7-12 years...or so) and be able to retain the original (expensive) finish for the full 25 years. The other thing to note: dogs claws require trimming 2-4 PER MONTH when working with hardwoods. This is what the hardwood flooring refers to as "routine" trimming. Some of my clients thought "2-3 PER YEAR" was "routine". I laughed. You have heavy, high energy, powerful dogs. A single lab can cause some damage over time. Two labs can do a number on a floor. Three labs and you have a very short lived hardwood finish. You have 7. I would find the most expensive, scratch resistant finish available in Australia. I would have the maximum amount of finished put your floors (you will pay extra) it and I would budget for a "buff and coat" every 5-7 years.

Thanks :) Yeah decided to go with tile. So sand cement is ok over existing tiles if I prep them first? Only problem is, the new pad can only be about 30mm at it's thickest (leaving up to 15mm for tiles) otherwise it'll end up being higher than the hallway floor. So I either need to make the fall shallower or not bother with the waste and make it all level. If I made it level, could I use levelling compound at that thickness or would deck mud/sand cement be the best option? Also, should I be putting in mesh for strength? (I know I should (and will) ask the local hardware what they suggest, but it's great to have suggestions from the Houzz community also)

We are a little biased, but wood floors are versatile, durable, clean, and timeless. Whereas carpet will eventually need to be replaced, high quality wood floors can last forever. You can install radiant heat under the wood floors if you are worried about them being too cold during certain times of year, and you can easily install area rugs over the flooring. Wood flooring is also more versatile than it has ever been so you can create any look. As an added bonus you can easily sweep and mop your wood floors, whereas with Carpet you don't always know what is lying below the surface. Good luck!