In message , at 09:52:24 on Fri, 23 Sep
2011, Mizter T remarked:
I suppose one other possible solution is if you could come to some
arrangement with Oyster customer services, e.g. pay the 40 pounds minus
whatever's left on the card, and then they'd keep the card on the
blacklist.

How does that help? It just leaves £35 locked on the card. While I agree
that the card will have thought it has £40 added, to OP doesn't say he's
spent any of it, only enough to get the balance down to £5 (or £45 if he
pays the £40 'owing').
--
Roland Perry