I understand the beam being installed when you did your earlier extension as that was an external wall, that's why I have suggested keeping part of the wall next to the island which was also an external wall, to support this, I will check this in the drawing to ensure it lines up for you. By opening up this wall as much as possible you are allowing more light back into the house The cost of running plumbing across I think is negative/comparable to moving the plumbing for the re positioned laundry and kitchen and removing any load bearing walls. Storage in the new kitchen is a big 2900 x 900 island of drawers for easy access, I have added a wall oven but that could become a 600 pantry with drawers in the lower part with a shelf above for small appliances. The wall with the TV could be a wall of narrow built in storage to be used in any way you need. This floor plan gives better flow between kitchen/family.dining/alfresco and better for unloading the car with the driveway running down beside the kitchen and verandah

Definitely looks interesting.. Excited to see the finished space!

You won't knock out walls for that budget. That is kitchen refit only. Don't brick up the sliding door, it will make the space impossibly dark and depressing. Better to just lock it and pretend it's a window. The real problem in that kitchen is that corner wall that eats into the available bench space. Is that hiding a water heater or something as it doesn't appear to make sense from the photo's you have. If Ii'm reading that correctly you could possibly move that wall outwards to free up extra bench space in that corner and enable a corner top cabinet. Toaster, kettle will fit there nicely. If that's within your budget I'd do it because it will fix most of the problems with your kitchen. When you have a small kitchen like this an easy way to increase bench space without structual changes is a nice kitchen trolley that increases bench space when you need it and can be parked over near the dining area when you don't. I'd replace the current stove with one that has an induction or ceramic cooktop. Because it's flush you can use the stove top as extra bench space when you're not cooking. Makes the space more flexible. Preferably put in a cooktop on the bench and separate built in oven rather than a freestanding unit. The integration will make your kitchen appear more spacious. With the small space you really do need top cabinets but solid doors are a bit claustrophobic so I'd go with a glass fronted upper cabinets so it doesn't swallow your space but still gives you storage. Also install under cabinet lighting this will help out with visibility when cooking at night. And if possible recess the kickboards to reduce their visibility or change them to brushed aluminium this will make the footprint appear more spacious.

my suggestion has the bathroom at the end without any changes to other walls, door or windows and i've include furniture to suit young long term student tenants and this could be altered to suit other guests...all the furniture, cabinets and fixtures are based on readily available flat pac options like Ikea and Kaboodle and the only custom carpentry will be the new bathroom wall and storage under the stairs and the usual trades for plumbing and electrical etc and i would use a shower cubicle rather than tiles so that you could use continuous vinyl flooring throughout the whole flat and minimise tiles...careful choices of all fixtures and fittings and maybe some basic DIY from your daughter and her boyfriend to assemble flat pacs and with painting? should allow the renovation within your budget and don't forget an outdoor sitting area with decking boards, outdoor furniture and a pullout clothesline rather than a dryer