Another question: I had some short cycling stories published in Singletrack magazine some years ago. Does the magazine retain the copyright to such an article (I received no payment) or is the author free to re-publish the stories elsewhere?
Normally (in the absence of it being spelled out formally somehow) a magazine just gets "first rights" aka first UK serial rights as per:
http://www.ukauthors.com/modules.php?name=Sections&op=printpage&artid=7
which means they get to publish it once (and nowadays typically also in a digital edition with the same layout as the print version) but you retain full copyright to your original material and are free to send it elsewhere.
Strictly speaking they retain copyright on any editing and layout work they may have done.
Payment or not shouldn't make a difference...
Sure they wouldn't mind you asking for clarification - if they're like me contributors are hugely appreciated and I very much doubt they'd mind you publishing elsewhere anyway.