To answer the previous poster:

When I called MBNA two weeks before my first anniversary with a request to cancel, the agent advised me that the upgrade vouchers would not post if I cancelled at that point.

He was very helpful and diarised an action for himself to check when my vouchers had posted and then to close my account. Which all happened, exactly as he promised.

I was offered 5000 points to keep the account open, but declined.

I was warned not to use my account between the anniversary and the cancellation, and, to my horror, an IHG charge went through to the Virgin card (when I'd actually got a BA Amex set up against that IHG travel profile -- there appears to be a bug with IHG's software where it can "remember" a previous card.) MBNA were understanding, and reversed the annual fee that got applied as a result.