HELP how do I get grey stains from white ceramic kitchen sink???

[HAPPYFACE]

I think it may be the saucepans or scourer pad that have caused them.I have tried the usual bleach and most kitchen cleaners etc
I've got people coming round next week and want the house to be nice!
Thanks in advance

woolies do a special paste made with silica sand
called JML spotless
I have cast iron pans and also get that problem
this stuff is teh dogs bollox

We've got some of this which works very well.

Oh thank you so much, I'm ashamed to admit I've left them on the sink for around 2 years!
I'm going to woolworths later to return something so I'll definately get some.

I use Shiny Sinks in orange bottle - it gets the grey marks from the oven trays off my white plastic sink - I assume it would be as good on ceramic.