Looking for something else I came across this reference in Len Scott and Stephen Twigge's
Planning Armageddon: Britain, the United States, and the Command of Western Nuclear Forces 1945-1964:
In August 1962, the Air Ministry approved deployment of an airborne command post "to ensure an alternative means of passing release messages to the Medium Bomber Force without recourse to landline communications"....To establish an airborne command post, a flight of Valiants was transferred from the tanker squadron and fitted with UHF communication equipment. Operation of the system proved problematic. Joint exercises with SHAPE revealed that UHF transmission failed to meet required standards of reliability. However, if HF SSB radio sets were used, no such difficulties existed...
I did not know there was any effort to create a UK TACAMO. Does anyone (Pontius Navigator? BEagle?) know any more?