I had the same problem months ago. The widening was caused by the chip inside getting dislodged and forcing the two halves of the key open. The key was replaced but customer services were kind enough to point out that I was only allowed one replacement key and I’d have to pay for any further replacements. Hopefully now the problem has proved to be more widespread, the tight buggers will relax their rules.
(anyone one else fail to keep a straight face whilst reading mudchute’s last post, or do I just need to grow up?)