I come in late as I have been busy. But my points are these:
1. Loss of Sub-Harpoon. This is no great shakes. It is not a weapon loved by the submariner. Launching a sub-harpoon missile against a surface target immediately gives away the submarines position. Yes this is true with Tomahawk but you wouldn't go launching Tomahawks from an SSN if the enemy was going to be able to do something about the presence of the submarine. The fact that you are using sub-harpoon itself suggests a threat to the launch platform.
2. MIOPS with T42. I have done MIOPS in the NAG with a T42 (HMS Exeter 1999-2000 deployment when I was the FC1). The sea boat was an issue and we made various recommendations following the deployment regarding the sea boat. It isnt and ideal platform for MIOPS but with adapt/improvise/overcome you can do that type of operation with a T42.
3. Sea Dart in the surface role - the enemy would have to be pretty close, but it is a big old missile going very very fast (remember Harpoon is subsonice), Sea Dart weight half a tonne and is going well over Mach 2. Going to make one hell of a mess.
4. Sea Dart is old but it is not as bad as some made out. HMS Exeter destroyed a Skyhawk flying at just 75ft in 1982. I was involved in a Sea Dart trial whilst serving in HMS Exeter but it is obviously highly classified.
5. CIWS and decoys provide good protection from most SSM's. Exocet was considered pretty much obsolete by the time I left the RN. The decoy systems and Phalanx are very good. The latest generation Russian SSN's that fly at supersonic speeds are the problem and T45 is claimed to be capable of dealing with them.
6. The main problem with T42 is now age. They are expensive to maintain and despite large reductions in crew numbers since conception complement is considerably larger then a T23.
The topic of the thread is off course SHAR. The government are taking an awful risk. Layered defence is one of fundemantals of anti-air warfare. We are getting rid of the best layer. The budget saving may look good to the politicians now, but if ships and men/women are lost as a result....