The one alternative is to buy an Oyster card before you arrive in
London - if you live in certain countries VisitBritainDirect will sell
you a "Visitor Oyster card" in your local currency and send it to you
by post. See this webpage for more information (confusingly it refers
to Oyster PAYG using its old name "Pre-Pay"):
http://www.visitlondon.com/travel/oyster/

I never knew that. But a quick looks shows the price is a *little bit
high* - in part perhaps because the GBP-EURO exchange rate used is what
it was not what it is (sob). A 10 GBP Oyster Card costs 18,45 Euro
including delivery to Germany. On the other hand, the UK needs the
money so please buy early and in bulk!

If you know someone in the UK you trust with your money, or who trusts
you with their money, it would be cheaper for them to buy an Oyster card
and post it to you. I know of no barrier to that. And if there is a
barrier I am sure someone here will educate me
--
Robin