Thank you for all your replies.
Whilst it is an interesting debate, I am not so much concerned with the merits of ADFs but whether the aircraft will need to have one installed.
As usual this business is so full of rumour and counter rumour.
I have written to the CAA and will be interested in what they have to say.
I have always found them very good in the past when clarrification is needed.
Bose-x - yes, you are of course correct so far as the DME is concerned which presumably will be around as long as VORs - which I guess is for a very long time!