The usual shambles
We could have bought the US Aegis System years ago which includes not only Standard missiles but also the Evolved Sea Sparrow Missile (ESSM) which is more capable against low flying fast targets. This system was perfectly adequate for Germany, Holland, Norway, Spain, Australia, South Korea and Japan and would have been in service years ago avoiding the cost of expensive refits to keep our ageing Type 42 destroyers in service.
But no. Building British whether it is value or not is always our first priority and if that's not possible then buy European to show what good little Europeans we are. For heavens sake don't by a cheaper, proven already available US system!
Just do a comparison between what we have got as our AAW destroyer and the US (given they are reportedly around the same cost per ship). Their Arleigh Burke Flight 2a class destroyers have twice the number of anti aircraft missles, two helicopters to the Type 45's one, their anti aircraft missiles can be used against warships whereas those of the Type 45 can't leaving her with no anti-ship missile system, the US ships have land attack cruise missiles anti-submarine torpedoes which the Type 45 does not and crucially for an AAW platform, they carry the Co-operative Engagement Capability allowing them to network tracking and targeting capability with other ships. The Type 45 might get this capability in 2014.
If the Type 45's anti aircraft missiles eventually work they will be better than the US equivalent but the US ship is far more rounded (and general capability across a number of missions is vital the fewer ships you have) and was available years ago. Alternatively we could have bought cheaper designs (such as the German F124) and had more hulls than the 6 we can afford to replace the 12 AAW destroyers we previously had.
Still, being good Europeans and putting civilian defence jobs ahead of military need is a much more important priority than properly equipping the forces.