If you go on to the Apple website and type in either the serial number or the IMEI number it will tell you a few things about the phone (is it still under warranty etc), one of those is wether the phone is registered or not (the majority are), which means that Apple Stores can pull up the address details.
They won't give the address to you (well, normally they won't, there is a way round it but playing it straight they'll say no) but they will call the person it is registered to and let them know.
As above, depends how much you want to do.
i cant get imei number the phone is pass coded. am going to try the sim in my phone and see if i can get a contact number from it, failing that i will contact 02, failing that then i will contact apple.
And yes i would like to retyrn it to its owner, as i would like someone to do the same if it was my phone they found.