Search the forum for Sony Ericsson Unlock and you should find the software. I'm pretty sure it'll work with the K700 otherwise there's places like http://www.totalmultiserver.com/
If the lead you have is a T28 service lead, then I have some software somewhere that will help you.
Not got it to hand, but it is called semc
the file name it appears as is SEMCTOOLv3.3_Crax0red.rar
might be worth doing a google for it......Busy atm