Things have got better.
http://www.ubercart.org/project/uc_global_quote makes it possible to allocate each of the hundred or more countries to a zone, such as the ones your post office uses when charging for parcels. I only discovered this a day or two ago and spent an Olympic weekend allocating every single country I could find on my post office's web site a zone.
http://drupal.org/project/rmzone was released yesterday by Andrew Foulston. Released for Drupal Commerce, it is not rejected by Ubercart and makes a data selector show-up under a Royal Mail heading (I discover that grey data on the drop-down menus is linked to other data selections, and forget quite how many clicks it took to find this).
Now, to get the last of my data out of ubercart global quotes I have tried disabling it and now even uninstalling it. And reinstalling it. Computer says no.