HI
Thanks to everyone who replied on this one.
I tried nearly everything but nothing worked until I did this SIMPLE SIMPLE thing.
I found the easiest fix to the problem. I turned off the Bluetooth connection on my phone. I think what was happening is that every 10 seconds some pulse goes out looking - and when that happens the headset gets confused as to whether it should stay being connected to the laptop or change to the phone - creating a short (200msish) silence in the headset.
So my simple solution is 'disconnect' the headset from the phone in Bluetooth settings while/before connecting to the laptop.
cheers
Karen