Thanks for the quick response!
I take your point on board, it certainly sounds valid. The site has been internationalised, so there is an English version among others, so anyone searching for English words should find the English version before say, the Spanish. These characters are also only on a few pages, so further down the hierarchy.
The SEOMoz web crawl came back showing these pages as 404's, but the likes of "Screaming Frog" came back with response code 200's.
Thanks again,
Stuart