FODPlod is right. With 6 destroyers and 13 frigates, there are enough to escort the carriers. The stated intention is to accompany them with 2xT23 and 2xT45 when in a high risk area. Long term you can expect to be able to deploy about a third of your assets - eg routinely 2xT45 and 4-5 T23. In a crisis you can "surge" in the short term to maybe two thirds - so 4xT45 and 8 or so T23. So yes the RN can escort the carriers, even in high risk areas, and have a couple left over for other things. Factor in the availability of allied assets (expect to see typically a French frigate and a US destroyer added to the group for deployments, and maybe one or two others besides) and things look better still. So it's not true to say we can't escort them.
BUT it's undeniably tight - I'm not saying everything is great, everything is too close to the limits, in common with other areas where numbers are clearly calculated by reference to the minimum needed. Take out some assets due to unforeseen circumstances (eg one of your few SSNs collides with something) and you have problems. There is an opportunity to address some of that that in the current review, especially if some modest increase in funding is secured. OK I accept that may not come about, but at the same time there is more of a political groundswell than I can remember. Committing to 8 T31 frigates (with maybe 3 of them enhanced for ASW duties) for example would be a relatively affordable way of easing the pressure considerably. Not a chance? Well, many confidently predicted there was not a chance of addressing the MPA gap, so let's see.