Of course, we can't have a different piece of artwork for the final spread - that would be prohibitively expensive. But there is an answer - there is an extra, single page available, after spread 12. The plan is to add back the joke for the British version, as an extra piece of artwork, on this final page.
There is something bothering me though: the actual 'thought-bubble' has been removed from around the fantasy lion. Without it, I worry that the reader will be confused. Now that the sleeping lion is no longer on the same page, there is nothing to suggest that this is a dream / daydream. It looks as though somehow he has actually swapped. Which doesn't make sense with the rest of the story. I have passed on these concerns. We'll see.
At the moment I am still working as best I can from an armchair, with my foot up, wedged under a bag of frozen peas, but next week I have the dressings off my foot and my stitches snipped. Come Monday afternoon, I will be able to put on a shoe (and have a shower!) for the first time in 2 weeks. I should be able to sit at my drawing desk too, at least for part of the day, so I can get on with the front cover artwork.