While on that topic, is it possible to register an Oyster at an
address outside the UK yet? When I attempted in 2005, the agent at
Notting Hill Gate seemed annoyed that I even tried.

I don't think so. I tried a couple of months ago and it did not work.

When I got mine in 2004 at Stratford, I just wrote my German address on
the form and they did not complain. Interesting enough there seems to be
no country field in the address shown online.

If they refuse to register you and thus limit your usage of the
Oystercard (no refund if lost, no monthly travelcard etc.) it is a clear
discrimination against Citizens of the European Union and thus illegal.
The European Commission
http://ec.europa.eu/comm/competition...sumer_liaison/
might be interested.

Martin