In message ,
Thunderbug writes

At the moment I have a soon-to-expire weekly Oyster card which I've
loaded £50 onto. Once the weekly pass expires my understanding is that
I'll have to use the big ticket machines to buy a paper ticket
(single/travelcard etc) and "pay" using the Oyster card instead of the
debit card I'd normally use. That's a slight improvement, I end up
with one £50 receipt to put into my accounts intead of 20 smaller receipts.

If you've loaded it into your pre-pay slot, you have the choice of
keeping it there until you can use it next year or phoning customer
Services for a refund.
--
Kat Women and cats will do as they please, and men and dogs should relax
and get used to the idea - Robert A. Heinlein