And who is going to provide the RAS outside CAS in the South East??
Luton, Thames, Heathrow, Essex, gatwick etc all too busy with there own airways traffic!! That just leaves Farnborough and Southend (Southend are primary radar only so harder to do!)
And yes, 5nm or 3000 feet isn't too easy in a busy choke point when the base is 2.4A! That is why we seldom offer a RAS - it is unachievable.