Right, last night I took the car out for a spin, and on the duel carriageway (of my private road ), when I went just over about 90mph, the red triangle came on. Nothing sounded out of the ordinary, so I pulled over and switch the car off and on again, and it went out and stayed out for the rest of the journey (all under the limit this time)
On the way back, on the same bit of road, it came on again when I got to a similar speed, and again went off when I restarted the car, and was fine the rest of the way.
Now from searching it seems it could be brake fluid level, but it wasn't flickering like it does for that; or auto spoiler (which has been removed) but the light didn't extinguish again which apparently it should.
So, any ideas?