monkey - that's not my extension!! It's a picture from the Chelsea flower show!! Mine is very much lower end! It's just I am having a pond a bit like that one!! I posted it to give a vague idea of the kind of look I was going for, that's all! 
I'm so sorry your finish isn't up to scratch. I don't have anything to say except
and we are here to support you as you take whatever action you need to.
For y'all worried about your weight - If it makes you feel any better, I have gained 70lbs in the last 4 years.
So 20lbs seems like nothing to me. Nothing! Once you have your house straight, and you have your headspace back, you will be able to spend all the time you've been spending making tea, chivvying builders, checking levels, and generally worrying on yourself. The weight will fall off. We should have a post-reno Self Improvement thread! A different kind of DIY!
Tatlerer - oh no re: the eczema. I wonder if it's the dust as well as the stress? I have this amazing stuff called Emulsifying Ointment, which is basically petroleum in solid form (I kid you not) that is unbelievably kind and gentle to the skin as a wash. It's very greasy but replenishes oils dragged out by dust like nobody's business. You can get a huge tub at the chemist for no money at all if it sounds like it would be helpful. I use it after I've been out for a long time in the garden.
whatashower - but your build looks lovely! If that's unfinished, I'd be happy to live with it!! 
monkey and fourmagpies For the driveway/garden - it will come right again, I promise. A couple of hours of getting up the worst - not now, when you're done and ready - works wonders. The amazing thing about nature is that it bounces back in the spring, reliably, every year. By June next year you will wonder why you were worried!! Everything looks so dismal over the winter anyway.
rick - you really, really shouldn't have to hire your own skip. But in the circumstances, it's a smart move. You'll feel much more organised afterwards.
Update from here - More blockwork going in here today. I'm having a square patio with a curved edge (if that makes sense!!) put outside the kitchen. Went out yesterday and the curve was totally and utterly wrong. I was freaking out a little inside, but managed to stay calm and have a conversation with the builder about what I wanted - he has put it right without complaining, bless his boots. I can see the rooms and the levels now in a way I couldn't a week ago. I don't know if this is just time standing in the site, or the fact that the walls are that much higher that the spaces are starting to feel like the ruins of actual rooms.