hide - how would you feel about another worktop? If you'd always be a bit sad you didn't have your Corian, I would wait. If you look at quartz or Dekton and think "ooh, this is the perfect excuse" I'd switch!! 
rick - It reminds me of the opening of Stonehenge by Spinal Tap.
In ancient times,
Hundreds of years before the dawn of history
Lived a strange builder, the Twatchops
No one knows who his was or what he was doing
But his legacy remains
I think the building regs thing might work in your favour if you do have to take the wanker through the small claims court. So it's probably worth waiting for, though I appreciate how much you must just want to crack on at this point in time.
extension - that sounds worrying about your neighbour's chimney. Is there any work-around that would still allow you to have what you want? Can you explain the concept/idea so we can try to think of alternatives?
Undercupboard lighting - you can get LED strips that are just AMAZINGLY thin. They're barely the width of a fabric tapemeasure and they just stick on. You need to hide a driver in a cupboard. I'm having one under an upstand nosing.
Question for those of you with modern open plan spaces - what lighting did you use? In the existing house I have a couple of white downlighting pendants, but I think they now feel too low and look weird. I don't want to replace them with spots, but I think I need something closer to the ceiling. Gah, I'm rubbish at lighting!