Thanks all, very helpful, some clear learning points for me here. First, I take on board the strong message that I should have informed ATC - I confess it did not occur to me at the time; in my defense I was only stopped for perhaps 10 seconds or less. Also interesting to hear that a helicopter hover taxiing may be talking to tower not ground. I will spend some time listening to radio chatter and try to get a picture of how this is handled in my local area. And it is true that in all my theory and practical training the word helicopter has never been mentioned! That does look like a shortcoming.
It maybe worth mentioning that the geometry of the crossing situation made it very difficult for me to see the helicopter - in a high wing aircraft with the crossing taxiway at a slight 'backwards' angle the helicopter was high enough to be completely hidden by my wing in my normal seated position. Not until I leaned forward in my seat and checked the crossing taxiway did I suddenly see it alarmingly close.
To be completely honest, if it had been a fixed-wing a/c, I would probably have stopped, let it past and not given it another moments thought! I would have seen it sooner, and am well used to dodging stuff on the apron. The fact that it was to me a 'flying aircraft' made me question what was really happening here hence my original post.
Finally I would add that as a student pilot (I was returning from a solo cross-country) I expect every day to be a learning day and I am pleased that I posted here and made sure that I learned the right lessons!
Thanks!
I was cleared 'Bravo to base'