Since Linton Chilcott is probably referring to operating in the north of Scotland when going VFR I will make a few points that are valid for this area of operation. Military traffic is more of a threat than Mr Cessna so I would suggest that in the remote parts of Scotland then this is when you would use TA/RA.
In the remote parts of Scotland then the Scottish frequency also doubles up as the FIS frequency so if the chap in his Cessna is going to talk to anyone then he will probably be on the same frequency (if they decide to speak). Traffic density is a lot lower then in the south east of the UK and TCAS is a fantastic tool for us when dealing with fast jet Mil traffic that is squawking. These aircraft will not be on the same frequency that you are on so intentions will be unknown and the Scottish controller probably won't have a chance of coordinating or finding our what he is doing.
Busy areas of airspace then TA only but I feel that TA/RA for the ops that Linton is referring to might be more useful!