DOUBLE AARRGGH!! Sorry, I just realised my simple, stupid mistake - I'd forgotten to link in the jquery.tooltip.css file in the HTML docs. Now I have done so, the tooltips work fine. D'OH!!! :((
So there's no problem at all. Thanks again to Jörn for this and other plugins, which are all the dog's bollocks as we say in Britland :o) I'm still curious about the positionLeft documentation, though. Cheers Fred