Well this is bloody embarrassing (spelling?).
I went out on the bike & started with No Route planned & on full zoom. Sure enough the map & icon stood still & weren't scrolling.
So I stopped & planned a route into Lincoln. Naturally the icon moved & scrolling started again. So I 'Stopped' the routing via the button on my map screen &, Bob's Your Uncle, the scrolling started again.

.
On the plus side Zooming right in & right out made no difference at all, the scrolling continued BUT this only happened with the 'dashboard' on the screen. As soon as I went into Full Map mode the scrolling stopped again
but a swift return to 'Dashboard' screen saw the scrolling return.
I'm convinced that it was scrolling on full map screen last time I used it so will have another play next time I'm out & about.
Edit: DRTBYK seems to have covered my thoughts above.
Edit 2. I do feel I should apologise to everyone for clouding the issue, particularly based on DRTBYKs post above.