In message , at 14:43:17 on Mon, 28 Feb
2011, Roland Perry remarked:
And I have to contact TfL in order to transfer the Oyster Credit to a
new card (or to otherwise rescue the credit if Barclaycard cancel the
card because I've been naughty, or indeed withdraw the Oyster-ness for
no reason whatsoever).

And I see that Tfl have a (very long) webpage about this:

http://www.tfl.gov.uk/tickets/15541.aspx

Here's what they say about "PAYG only" OnePulse cards:

1. Simply continue travelling until your credit is used up. Your
original Barclaycard OnePulse card will still work as an Oyster
card after the credit card expiry date. Be careful to keep your
original card separate from the new one when you travel to avoid
the wrong card being charged.
or
2. Transfer the balance to your new Barclaycard OnePulse card online.
or
3. Request a refund at a Tube station. If you can't reach a station
easily, you can send your Barclaycard OnePulse card in to us at:
Oyster helpline, 1st Floor, Albany House, 55 Broadway, London
SW1H 0BD.

If autotopup is enabled, they in effect offer only (2), with several
extra hoops to jump through during the period between the new credit
card arriving and the ols one expiring.

It's all a huge palaver, and miles away from the potential "best case",
which would be for the old card's Oyster component to be frozen at the
same time as the credit card expires, but be transferred automatically
to the new card the first time you touch in with it.
--
Roland Perry