It may all become rather academic in the next few years as quite a few of the UK NDBs have already been withdrawn, with a few others effectively withdrawn although officially u/s. I certainly can't recall any new NDBs beng announced. Maybe we'll find the requirement removed when they realise there are no ground stations left?
Personally, considering the volume and complexity of today's CAS, I'd prefer the accuracy of VOR/DME and GPS as belt and braces back-up to visual navigation. Although the receivers are handy for thunderstorm detection - as well as the cricket!