Tiles are good IF they are at least 5 mm thick, unglazed and will withstand
the severe thermal cycling inherent in a simulated hearth oven. If you use
Google groups search to find postings on hearth ovens, baking stones,
quarry tiles and similar terms in the newsgroup alt.bread.recipes you will
find more information than you want or need as well as some bitter
arguments and gross paranoia about lead in ceramics.
I bought my 2 pizza stones because they were on special offer - if I were
starting anew I'd go the tile route.
John
p.s. Yorkshire is the best part of England to live in - and I wasn't even
born there.