Hi Chris,
http://en.wikipedia.org/wiki/Mobile_phone_tracking http://investigativeresources.co.uk/ http://www.mobilelocate.co.uk/ http://www.traceamobile.co.uk/ http://www.planetcreation.co.uk/sat-gps/ just read and choose wisely, because some of them need the phone user to respond to a text to enable tracking.
or you could try
http://www.squidoo.com/trace-mobile-...reverse-lookup this apparently gives you the option to get the registered users name & address.
I've not tried any of these, just been recommended them by someone who runs a business and uses some of them extensively.
Good luck Chris,
John.