Shy, I did overstate the case. I saw the part about your being for GPS development, but still don't understand the connection with the CAA's worries about unauthorized approaches and ADF.
Don't know about the UK, but to be certified for IFR in the US, any GPS unit is required to have RAIM capability. If it doesn't provide the warning, it can't be used for IFR. I would assume the same requirements exist under JAR.
In order to launch IFR offshore using the GPS, I'm required to have 2 VOR's, and both must be operational. My plan if the GPS fails is to dead-reckon to where ATC can talk to me & get radar contact, about the same time I would start picking up VOR signals, perhaps later. Exactly the same plan with or without an ADF, since the ADF won't help me much here. I could home to a commercial AM broadcast station, but to what point? I would then fly the ILS to my home base, which has no LOM, thus the ADF would be of no help.