Those who assume the carriers can be sold need to have a think as to who will buy them....
Agreed, it's unlikely there would be customers falling over each other to outbid their rivals for the ships. If sold as carriers, or any other type of active vessel, it's a racing certainty they would only get sold if they were a 'too-good-to-miss' bargain for the purchaser. We would have to brace ourselves for more '
They cost us £x and we sold them for £x - 90%' headlines.
Speculative purchasers for a not-to-be-missed bargain might include Japan, South Korea, Australia, India and Brazil. I'd bet that a Korean shipyard would do the needful on converting to cat and trap, or any other conversion for role, at a price that would still make the whole deal an absolute steal for the buyer.
And, of course, the UK wouldn't be selling them for the the cash it gets back, it would be because of the cash it no longer has to splash out to operate and maintain a full carrier capability. Not what I want to see, but a very real possibility in my opinion, whether sold on or not.
Edit:
Forgot the need for Europe to beef up it's capabilities now Uncle Sam is back off to the Pacific, so they could become a European capability. Still cheaper to get any mods done in Korea but that would not be our call once our European allies are calling the shots and get themselves organised. Somewhere around 2050, perhaps.