urgent help! my phone is stuck on loading bar after ios7 update

hi everyone, I need some help!

I have the iphone 4 - however it hasn't been backed up in ages due to not having enough storage, so today at about 12pm uk time I bought 20g icloud storage and then I plugged my phone into my work PC.

It said it was doing step 1- 7 or whatever of update, I seen it saying verifying update, verifying firmware etc.

then it updated some of the apps that came up....then my screen went black and the apple logo came up with a little bar under it, the bar has moved a tiny bit but has been stuck at the same place now for over 3 hours!

I was on IOS 6.1.3 before this, what do I do!? I don't have a laptop at home and I finish work in 3 hours and I need my phone please help!

thanks

Lisa xx