"(If you put the seat full to the bottom,
for both height and inclination, it should stop
the rocking until they fix it. )"
Cheers Nev - it was already at bottom height, and this morning I wound it down to bottom inclination and no more rocking
I'd prefer it to be inclined a little though, as I do feel as though I'm going to slide forward every time I hit the brakes, but at least the rocking has stopped for now! I'm still going to push this with the dealer though, as it's clearly a widespread problem and not acceptable to put up with in the long term.
To answer the question about "red herring" boot release problem...
When I first got the Brera, on several occasions the boot would be "popped" open when I came to get in the car. No alarm, no breaking detection. To cut a long story short - the problem has never recurred since I took the keys out of my pockets each time I get home (clearly the button is way too sensitive, but I've got in the habit of putting the keys on the desk when I walk in, so it's liveable with).
PS: If it's any consolation, my missus used to have a Mini and had no end of trouble with the seat folding mechanism, and had to have it replaced twice under warranty, and then once outside warranty
. We only had the car a couple of years - so much for the legendary BMW build quality!