John S, A man after my own heart - sniff the stuff and test the olfactory memory banks. Citrus cleaner may well be it then.
Mike, True, its the citric oil we need, although citric acid does work on mild rust but I would get shot using up her lemons for that.
JH, thanks Jiff is readily available at the local supermarket and well worth trying.
I shall add it to my other cleaner isle standard - "Gumption" abrasive cleaner that works well in lapping the bore of model cylinders. Real cheap too as I nick a bit from the wife's cleaning supply. hmm, better check if she has some Jiff in there too.
Shame really, "Gumption" and "Elbow Grease" would sound rather good together. Trouble is, with the normal use of elbow grease as one gets older its supply diminishes.