No.
No.
No.
IMO, they have actually been surprisingly sensible about making roads exceptions to the new limit, so that most through roads with good width and visibility are still 30.
It makes a little difference to journey times, but not too much in my (very limited so far) experience. I don't think they have started enforcing the new limits with fines yet, though I don't imagine it will be long before they do.
One thing I had already noticed due to existing 20 limits though, is that my car really isn't designed to go that slow. In 4th gear (out of 6), it will be doing around 26-27 without my foot on the throttkle. I have to go down to 3rd before it will be about the right speed with no throttle, and even then it is borderline.