WD 40 on mirrors make sure to wipe on sparingly. I reckoned spots on disco was due to brake dust particles. A Present :2008 TDV8 HSE
Gone Audi A5 2.7TDI
Gone Discovery 3 HSE
Gone Mercedes CLK
Gone Range Rover 2.5 DSE

Echoing what I imagine Johnnys point would be above, I used to see this fairly often in cars that had been parked in railway station carparks, where the trains are slowing into the station. Small hot metal particles from the train's brakes in the air.

I used to work a very long time ago for a Fiat dealership. Some of the new cars we used to get there suffered from this exact problem. Small rusting iron particles, fortunately in that case embedded in the travel wax the new cars used to come in. It was traced back to this cause. Lloyd Barnes

Current
Crendon 427 Sideoiler Cobra in build... 7 litres of madness!

Gone
2008 TDV8 Vogue - Black with Ivory/Grand Black Lacquer
2008 VW Touareg 3.0Tdi
6.3litre Dax Cobra - 12.34 Second 1/4mile at 114mph

Durham - glad to see you managed to get rid of the spots with a simple solution.

The car I'm looking to buy seems to suffer from something similar on the bonnet - small round particles of rust (not sure if they are embedded or just sitting on the paint - was too cold to stay otuside for long)... hopefully they are just on the surface and not a sign of hidden rust on other areas. Will speak to the dealer when I go to pick up the car and let you all know.