The reason for using an NDB as part of an RNAV IAP in the case of Shoreham is historic. When the CAA trialled RNAV(GNSS) non-precision approaches those aerodromes that took up the offer had their approach designed by the CAA for free.
As a cost cutting exercise the beacon was used instead of a new RNAV waypoint.
There are a number of older LNAV only approaches which are being upgraded to LPV and the opportunity to dispense with ground-based Navaids is part of that work. (But not funded by CAA)
BTW there are plenty of people at CAA who understand RNAV including me when I worked there. Yes there was a preponderance Vulcan and Tornado Navs but they have all retired now.