I reckon within 5 years we will see ASW capabilities on unmanned aircraft and once again the UK will 'miss the boat' (pun intended) and be left behind the rest of the aerospace world.
I've been delivering networked computer systems for a very long time, and it would seem you are at danger of falling for the simple == cheap argument that defence suppliers use.
If one looks out of the office window it is a simple task to confirm or deny the presence of a quadraped (dead or alive) in the car park with a high degree of certainty. Doing the same task from the window seat of a short hop aircraft as it banks over the long stay car park is also simple.
It is however fantastically expensive to do the same thing with an automaton. Even then the degree of certainty may not be what you might wish for if you are planning on engaging with said quadraped.