I have a new computer and, thanks to crucial tip from medievalist, it's working just as it should be working! Instead of just being good for the PhotoBooth feature, it's now a usable replacement to my old laptop whose logic board is fritzy enough to not be usable for much anymore.
I left my jacket behind at Heathrow, and it never showed up in Lost and Found there - but I've replaced it now, and the replacement arrived.
The seacoast isn't all so far away when there's a car handy to see it in. We explored Maldon, a scenic boating town with a healthy representation of shops and huge numbers of takeways near the seaside park, this afternoon, and towns around it.
It's good to be home.