Do you know whether people not living in the UK can register their Oystercard and use Oyster online to buy tickets?

When I tried to register a few years ago, a UK postcode was required, which I can't give since I don't live there.

Meanwhile the registration process has changed. TfL now ask for details of the most recent journey in the past 8 weeks. Since I can't complete this step until day 2 of my next visit, I wonder if I'll be able to complete registration after all.

Thanks in advance for your replies.
JoH