First of all, I'm not knocking the purchase of carriers by the UK (even though I don't think we can afford it!).
However, it strikes me as pretty obvious that if as a nation you happen to have 11 carriers, then you can maintain 5(ish) continously at sea at several strategic positions aound the globe.
If you only have 2 (and probably only one active airwing) then you will do no better than having 1 available most of the time, and it is a distinct possibility that it will be in the wrong place when you do need it....
That doesn't mean that you shouldn't have a carrier, it does mean you should be honest about all the issues involved in having one - GOOD AND BAD!