This is the outcome of the British Government's massive cuts in defence spending - goodbye Ark. It was all over the BBC news recently. I thought I heard wrong when they said the Ark was to go, but sadly that was not the case. According to the article in the link I posted she's due in Portsmouth on December 3 to start the decommissioning process.
The Illustrious is supposed to have been already decommissioned. There has even been a spoof posting of her being for sale on eBay! I'm not sure what Ocean's fate will be.
Sure these ships are over 25 years old - but the RN is being stripped of its air capability in very dangerous times!