Not_a_boffin,
I agree that we need a complete range of systems to provide adequate defence, whether this be Navy, Army or Royal Air Force. This need includes aircraft carriers (with aircraft).
Unfortunately there are many items missing, including LRMP, sufficient ASW asets, sufficient air defence assets, sufficient submarines, manpower etc. It therefore comes down to what provides maximum protection for the money available. The system must be robust. I really don't feel that the aircraft carrier are it.
As for a coastal fleet. I do feel that we need to increase the size of this.
It will be interesting to see what does happen with the aircraft carriers and the aircraft that should go with them.