Thanks for the replies guys,

I had tried Brasso, with a rag and clean...no different...I also tried Meguaires chrome polish, which helped a little but those stains still there.

I've given the Oxalic acid a go.  Unfortunately I've only got a big nappy bucket to put it in (with 4-1 mix) I cannot soak the whole ramp, so I'm just doing the ends and 'baisting' the rest of the ramp!