Its very true to say that our defence capabilities will be greatly deminished with the phase out of the F111. Even if the JSF is brought into service on time it still leaves a very large gap in our defence. An increase in tanker numbers (and pilots on speed) would act as a force multiplyer but he fact is we will still not have a long range weapons platform. Just remember the F111 strike capability can be weighed against the likes of the B52 so the introduction of a long range strike missle will fulfill the gap to only a point. (75% seems to be the number as above).
I have a feeling we will be letting the US onto our shores in the form of "training bases" in the not to near future. its begs the question: how much is a alliance with the US worth on a world scale.
It must be remembered that the cost per flight hour has been greatly decreased rather then increased in recent years especially with thimplementation of the cold storage facility etc. The ability to support and maintain the F111 into the future has become more reasonable however the FB-22 sounds like a firm contender for a replacement.