Ideally you would want 900-1000mm clear space in front of your vanity and for walkways, unfortunately we don't live in an ideal world and have to work with what we have. 700mm would be the absolute minimum width for a walkway to still allow reasonable passage, although I would be reluctant to go this tight. A floating vanity will help the space look larger and storage can be included in a mirrored shaving cabinet or mirror with shallow shelf above the vanity.

LOVE that you noticed the vanity over the bath..a feature used in all my own bathrooms as it provides so much extra counter area, improves the look of the whole vanity and the space on the end of the bath under the extended counter is perfect to line up all our ducks (the same idea also goes well over a toilet)...BTW i noticed that i forgot to include an in-wall mirror doored medicine cabinet with the outside doors hinged in opposition (so you can see the back of your head!)... the medicine cabinet could be as wide as the vanity counter and built in wall 150mm deep with adjustable shelves is suitable for almost all bathroom storage including toilet rolls and with all that extra in wall storage it's worth considering a wall hung vanity that will allow floor space underneath for a waste bin, dirty clothes basket, set of scales, slippers etc and makes the room feel so much more spacious...best of luck with your new bathroom, the next challenge is which tiles and taps and soap dishes and towel rails etc etc??

You can get slim range hoods that generally fit into the wall cabinets ours were approx 40cm deep which housed the complete operation, our plumber ran a 6 or so inch flexable ducting into the roof cavity and out under the eaves. Most brands make these. A photo would be helpful. https://www.thegoodguys.com.au/omega-52cm-undermount-rangehood-oru50x?CAWELAID=620013790000422290&CAGPSPN=pla&CAAGID=21711678566&CATCI=pla-376401441757&gclid=CjwKCAjw0qLOBRBUEiwAMG5xMNN63iJr0n0Bnxf31-Gt0t5s0vERt_lOwOYkC6uzovf9TDWwawry9RoCgxQQAvD_BwE&gclsrc=aw.ds&dclid=CLOv9erawdYCFc0slgodE5oLHg Where we didn't have wall cabinets we had tall boxes of stainless look laminate built up to the ceiling which contained the extraction unit, which was approx 30-40cm's and extraction ducting cheers

K_jossie, there's some really helpful suggestions here. I can't add much in terms of design ideas, but in a small kitchen that serves a family it's vital to maximise storage, Have a look at some of the more novel ideas for extra storage. You can put drawers in kickboards for things like baking trays, serving trays, shallow casserole dishes, serving platters you don't use often, etc. Loads of space there that usually goes to waste! Another idea I saw that I thought brilliant was making walls into shallow storage. Where you have a blank wall that it isn't practical to place cabinets against, and you don't plan to put furniture against (such as along corridors or walkways), the lining can be removed between the studs and shelving inserted and sliding or hinged doors fitted. It provides shallow storage that is brilliant for things like canned and packet food, cups, glasses, and some of the utensils that we typically like to hang in the kitchen. I also saw this method used above a child's desk area, using the in-wall space for storage of art and craft supplies. I agree a slideout pantry is a fantastic idea. I had one in our last house and loved it. It provided loads of storage in a very small space. The other way to maximise storage is to use drawers extensively instead of cupboards. When designing my kitchen, I made a list of things I needed to store and designated their future home on my plan, working out both where they were most accessible when needed and also the optimum way to structure storage space to hold everything. It's amazing how much difference just varying drawer depths according to the height of items to be stored in them can make. Best of luck with your extension. I hope the result is pleasing.