Hi Samantha, Interbath has a range of square and round shower heads, but not as big as 500mm. The closest size we have is 300mm, but with an ultra slim showerhead. You can find our products in any Masters or Mitre 10 store. Interbath Showerheads

Depends on what type of shower you prefer, if you like a good needle like strong shower flow on your skin go for round, if you like a feeling of being in the rain go for the square. The smaller the shower head the stronger the flow, with the exception of the wand like shower heads and telephone type of square shower heads, they are weak. We went for a large square shower head in our new home build. Also don't forget the water pressure in your house as that is another factor to take into account, if it is weak then you will have a trickle!

you'll need a plumber to check the existing pipes but you may be able to access inside the wall from an adjoining room (easier and cheaper to replace plasterboard than tiles) and be able to add a new shower with a reachable shower rose as well as a handheld but i hope you have a few spare tiles or can steal some from a less obvious place ...best of luck with the plumber but research suitable new showers with handheld and adding the plumber's time and repairs expect at least $2-$3 thousand but well worth it for a more comfortable bathroom

Would you consider two mixers, a lower one for the bath and a higher one for the shower so there is no confusion for visitors? Safety and ease of operation should be the highest priority when looking at mixers for shower/bath combinations. If you only want to have one mixer then make the height suitable for somebody having a shower. You don't want to be bending over to adjust the temperature when showering in a shower\bath. I usually design bath mixers and spouts centered on the wall of the long side of the bath so if you need extra hot water when you are having a long soak it is easy to reach. I have never heard of the requirement for a bath mixer to be at 700mm, although this could be a good height for a bath spout depending on the depth of your bath. Best of luck with your new bathroom, Dr Retro of Dr Retro House Calls