I agree with Spitoon & Rej.
It's an absolute that you do not descent below RVA levels (and all radar units in the UK have them).
Besides, using Finn's example, if the boundary to drop out of 5000ft is 20 n.m from the airfield, why is there any rush for further descent?
By my calculation, using a CDA (see other thread) passing 6000ft for an airfield 20 n.m away would be sufficient to get the height off....better still if the airfield has any significant elevation.
Tori