I'm pretty sure Obama told Cameron on his recent visit not to even think of going back to the B. If it was going to happen, the announcement would have been made as scheduled a little while back. The US has plans, it is shifting focus to the Pacific region, and needs it's 'Allies' in NATO to pick up the slack in the European theatre. That means they will want us to put BOTH CVFs into service, as Cat and Trap, with F-35C (though the USN may well supplement the air groups with sqns of their own from time to time). A three carrier Euro force (including CdG) will allow the USN to comfortably redeploy two or three CVNs to the west coast.
So the ConDems have had their chain yanked by 'His Masters Voice', the US, which has put the kibosh on Hammonds plan for short term savings/long term cost increases that would inevitably result from such a U-turn. No going back, they have been told, you WILL buy the 'C, along with the EMALS and AAG, which has lead Cameron to order this 'review' as a way of buying time for his minions to come up with a plausible excuse as to why they aren't changing course (back to the B) after all.
