Some very good points have been raised in this difficult subject.
Have some people though actually forgotten that we are an island nation that is extremely dependent on the sea for our imports to survive? (In fact, probably even more so today than we were during World War 2, as we now have much less available UK manufacturing, farming and fuel resources to draw on, etc!)
Can some people also actually imagine what it would be like to be on any merchant or RN ships that are well away from our UK shores with very little (if any) air support available from our RAF. The situation would not be so bad if the RN had some more capable ships and submarines to help defend itself with, but there are now even fewer of them available to carry out such important escort work and patrols in what seems an ever increasingly dangerous world.
Aircraft carriers are virtually self contained mobile airfield that could and should be capable of operating a wide range of aircraft wherever they are required around the UK or indeed the world. Such aircraft can actually take the battle to the enemy, rather than our current few RN and RFA ships having to try and defeat incoming missiles threats with mostly close range machine guns, and if they are lucky, perhaps with the aid of a relatively short range missile system.
This country does require proper aircraft carriers that have catapults and arrestor wires to enable a wide range of UK (and other friendly nation’s) aircraft to operate from them when required.
If the UK ever becomes the victim of any direct air attacks, then the current few RAF airfields would basically be immovable sitting targets. However, if the UK has very capable and flexible floating airfields (aircraft carriers) then these could be moved (as required) to counter any perceived threats. For example, if required to defend the UK, they could be positioned well out to sea off the UK coast to help provide a proper outer layer of defense for this country, including its RAF airfields. If however that floating airfield was required much further away from the UK, then those carriers can also provide the flexibility and capability wherever it is needed around the world. (This has previously been required and very well demonstrated by this country and many other countries during numerous wars/conflicts!)
Also do not forget that when required, our Naval aircraft can even be completely detached from their Carriers to operate from UK airfields (or anywhere else abroad), as perfectly demonstrated in Iraq, Afghanistan and even during the Battle of Britain, etc.
In summary, in my humble opinion, if this country truly wants real flexibility, capability, cost effectiveness and the ability to survive threats to our vital imports at sea, then we do need some real Aircraft Carriers and the expertise provided by the FAA to counter threats outside of the range of Typhoon/Nimrods, etc. Likewise, if many of our land runways get taken out in a war then it is aircraft such as the Harrier that could remain ideal to help defend our country and forces abroad by operating from roads, forests, small warships, etc.