We just spent a few glorious hours or so trawling the internet and writing old skool jdbc code, to discover this little beauty. Simply upgrade to 10.2.0.5 of the jdbc driver and it goes away.
Thanks to this post http://efreedom.com/Question/1-377745/Oracle-JDBC-Euro-Character we discovered our problem.
For the full details on the euro….
And if your really bored: