NATS do have a commitment to provide certain minimal navigation, as witness the consultation etc over the withdrawal of the NEW VOR.
Keyword here is minimal I fear and although I don't have a copy of the NATS licence to hand I recall that the navigation that has to be provided is to support the en-route services that the licence covers.
Sadly, time does not permit further research just now - I'm being dragged off shopping.
Maybe later......