Thanks a million, Martin, and you're right about Athlone. I'm sure they don't teach that poem anymore, it's a far too 19th-century-romantic-nationalist effort to show that we too had our heroes on bridges (just like Horatio, Napoleon etc.).

For anyone else who happens to browse this thread, here's a site run by an Irishman whom I met a few years ago that gives some information on Sarsfield and the Wild Geese.

And here's another, run by a US-based organisation.

Both are enthusiasts' sites, and I can't vouch for their academic standing. If you want to research folk songs about the period, do a DT/Mudcat search on Sarsfield, Wild Geese or Aughrim, and you'll probably get more than enough to keep you going.