How do I bathroom / kitchen / extension? etc.

I'm almost done now, but I have had quite a few learnings along the way:

LVT - They say some varieties can tolerate subfloor imperfections, but not as well as they make out. Its pretty smooth and level, but I can feel a bit of flex/hollow feeling in some areas.
In hindsight I would have liked to self level the whole area up to the hallway, but was budget/practicality/time meant not.

Screed - I didn't realise how long it would take to dry. Had knock on effects on ordering kitchen, choosing and ordering flooring, and organising contractors later. When a builder says they'll have built your extension in 4-6 weeks, I naively thought we'd be able to get in and fit kitchens, decorate and move in soon after. Add 40 days of screed drying, then lining up kitchen measure, kitchen fitters, flooring and it takes quite a bit longer until its usable.
I started the extension late May, and hopefully will have the gas hob connected and gas signed off, kitchen sink plumbed in this week (approx 4 months). Decorators coming end October.

Living without kitchen/boiler - Pretty grim. The wall knocked down in the above picture was where part of my kitchen was, and you can see the boiler on the left. That all came out beginning of June. New boiler was commissioned and kitchen installed beginning of September. 3 months without a kitchen and immersion heater water, and no washing machine with a 5 year old and 18 month old was challenging.
I'm extremely fortunate to have been able to buy my mum a small house walking distance away last year (having family close by for both our and her health and mental wellbeing was a big priority with Covid uncertainty) and we've had huge support with running washing loads, some cooked meals, washing children, childcare etc.
The kids have been fine really, but I think only because we've been able to drop them off to grandma when everything got a bit too much. Both myself and my wife are rather worse for wear, health, diet, stress levels etc. Will be glad for it to be over. Mental load is very high.

Garden: Wrecked. Builders were pretty good and tidy, but 4 months of diggers, material storage, scaffolding, heavy foot traffic has wrecked it. Landscaper coming this week to relay patio, level everything and returf as the grass has now been overtaken by weeds and is unsalvageable.
Also, In hindsight, I would have done the slabs at least much earlier, as the bottom part of the white render is showing the effects mud, sand splashing. Hopefully it will clear up with a jet washer.

Budget: We have miraculously stayed pretty much on budget from our estimates at the start of the build. We started just as the materials shortage / price increases were coming in and our builder was extremely good at sourcing materials, windows, bifolds and them arriving in time.

Work distraction: I get very easily distracted, and quite nosy, so I've not really got much work done in the last 3-4 months. From getting stuck in to help where I can without getting in the way, to going back and forth to Howdens etc to make sure the kitchen fitters/electricians have what they need on the day, so they don't have to come back in a week.
My office is downstairs just by the work going on, so extremely noisy and I found it difficult to concentrate on work. Also with the office being a dumping ground for stored kitchen stuff, it became a horrible place to get work done.
I should have got a bigger storage unit and dumped all the decanted kitchen stuff and boxes in storage.
Self employed while working from home during an extension is not easy.