Any missile is very subject to jamming/decoys once the primary sensor provider has been knocked out. Also while the speed of missiles is impressive the response time of modern SAM's is equally impresive. I hope you are aware of that?
Speed may sound like a massive barrier but ultimately it is the anti-jammer technology, the stealth/evasion capabilities and the targets radar lock that are the big players in a missile engagement.
SAMPSON/ASTER would probably knock out a missile traveling 5x the speed of sound as easily as one travelling 3x the speed of sound.
It is when a missile is close to the sea that it becomes harder, or of course when there are 30 of those missiles... In that same respect though Sea Viper can rippled fire 10 Aster missiles in 8 seconds. Coupled with the ability to keep the missiles "in the basket" and the range and power of Sampson it is going to take more than even 8-10 Bharmos to definitely kill off a Type 45 that is aware of the threat axis.
Of course if you are engaged unprepared, without knowledge and from an unexpected threat axis then no amount of technology will save you and the opponent will probably be able to sink you with even an old WW2 torpedo because of the advantage that surprise and stealth can provide in the naval game.