I did repaint mine once using the techniques suggested above and the tub surround was in the same condition as yours. It lasted more than 10yrs. Make sure you sand the rust right back if you can. Also suggest you tape newspaper around the entire area (floor, walls, doorway, stainless top etc) as the overspray from the paint will travel and make a mess.

if you mean a double laundry sink with two holes then they are readily available but also consider having the waste water from the washing machine fed under the sink directly into the drain...very common and looks good but you need to discuss with your plumber to get the best result

i would have a 750mm cavity slider between laundry and scullery for better hygiene and noise control but location of all sinks, stove and fridge depends on how you plan to use the kitchen, island and scullery and do you want a wall oven, wide cooktop, built in microwave etc will you use appliances in the scullery or kitchen, are the cooks right or left handed as that will help decide best location for DW but my first suggestion would be to move the sliding door in the laundry to allow for wall to wall tall storage for cleaning appliances ironing board etc and there's space for front loading wm and floor mounted condensor dryer, drop in laundry tub in a wide counter and underbench space for a tall laundry basket and wall cabinets for cleaning products and a hanging rod but the laundry and scullery counters could be deeper for more useful work surface and neater under counter wm space and i would lose the small return wall in the scullery as it cramps the work space

@wuff, Thank you so much, and congratulation for your renovation, I wish you will enjoy it for so many years to come. Yes, I agree living into a granny flat next to my son was my husband wish before he passed away. It is good to be close to family. Also I love the suburb which I have been lived in for 22 years. My Daughter and her family is living close by too. Most of my close friends are living around and we always gather for a brunch, or lunch or watch movies. The good thing is most of my friends pick me up and don't let me drive most of the time when we go out. Thank you again