Thanks Bula, tried again with redsn0w and have managed to get it into pwned DFU, so now should hopefully be able to get it working again! Thanks for making me persevere :)

I have an untethered jailbroken iphone 4. I tried to remove the jailbreak and update the software, but it didn't work. Anyway, long story short, stupidly I used the 'erase all data and settings' function on a still jailbroken phone. It's currently stuck on the apple logo. I can't get it into DFU...