OK something weird is going on here. In my question (subject headed Group / ungroup). I asked how to group an audio and video clip back again after ungrouping them.
The answer - simple, slect the tracks and press G or right click, select group and create new.
I just had to do this again and I selected the video and audio track - by clciking on the grey separator between the two tracks and dragging along until the whole selection was 'blued'. The pressed G - nothing, tried again and did the right click \ group but the 'create new' was greyed out.
I did it the first time, I am guessing it is somethign to do with the way I have selected the two tracks but - Jeeez banging my head here!