Does anybody actually use VFR advisory routes in the UK? It seems utterly pointless. Any pilot should be able to get the map out and plan a route which is outside Class D. One needs nothing less, nothing more. Sometimes a transit of D is worth asking for, but if one doesn't get it then one has to fall back to the original plan.
It's different outside the UK (where CAS transits of C or D are generally much more freely given) but an IMCR holder can't fly IFR there anyway.