OK - initial trials were not as good as I was hoping:
Motorway:
Telephone untested - too fiddly with winter gauntlets to try and press the call-answer button - summer gloves should be ok. (It is possible, but difficult to "touch-feel" for the right button.) With practice , obviously, your hand would go to the right place - I can change volume/mp3/radio. Just the time element of picking up the phone before the call minder kicks in.
MP3 - too much wind-rush to hear properly - volume needs to be up so high that the higher frequencies are painful.
Radio - voice ok, music as per mp3. There is an issue with signal strength - it's probably just the area I bike through, but the jury is still out on how good the built in aerial is...
Everything is much better on normal roads, obviously due to lower speed/less wind noise.
I still need to try a couple of things, and for the record this is done without earplugs which I don't normally wear.