Well, a bit of an update. I left it for a while in case the affected area had gone soft or something, but the Autosol still wasn't doing it. This made me think even more that it was the solvent in it causing the problem, as it does smell a bit petrol-like. So I tried something with a fine abrasive but no nasty solvent. So, toothpaste it was!. At first it seemed no better, but a bit of elbow grease brought the shine back. What a relief, and minty fresh too!
I count that as a good save, and free too. Hope this may help someone else in the future.