Upon turning left the noise came from the right hand wheel arch area. l inspected the area, could find nothing, then drove the car at full lock either direction as quick as possible. Grind disappeared after 2 minutes, and has not come back so far. Any ideas what it was?
l have done, Carole, and it seems OK. The car is 4 years old so mechanically should be reasonable. It sailed through its MoT.
Ivortskivor - yes, l checked the mud flaps and also the rubber skirt at the front of the Astra is (& Corsa's) - all seems OK.

check the coil spring

Possibly the noise was either a chipping caught between the brake Disk and calliper or the disk shield.
Vauxhalls are also known for binding brakes caused by sticking callipers.

sounds silly but entertain me do you have mud flaps if so check the bottom of the flaps for signs of it scraping of the ground the surface at he bottom of the flap will be rough if its been hitting