3GS Stuck in Recovery - Please Help Me!

Hi,

I've just upgraded to a iP5 and wanted to use my old 3GS as my works phone, so i thought i'd do a quick restore, unlock it from O2 and off I go. No such luck. The 3GS had been working fine since day one with no problems at all. I downloaded an IPSW file for IOS 6.1.6 after the normal method kept corrupting and plugged the phone into iTunes. It quickly extracted the files and seemed to be going fine until the restore when it hung up at about 20% of the blue bar. I tried this several times and the same thing happened. I've now spent nearly 8 hours trying Redsnow, Recboot, Fonepaw, Tinyumbrella, iTunes and various IOS's, but nothing works. Still stuck with the 'Connect to iTunes' screen. I've tried DFU mode and Recovery mode but nothing works and i'm tearing my hair out!!

iPhone 3GS, iOS 6.1.6