please help: nexus 4 lollipop install wont complete

I updated my Nexus 4 to Android 5 lollipop last night using the OTA update but the install process just won't complete. It has now been on the "installing system update..." screen for more than 7 hours! The status bat has been complete for at least 6 and a half of those hours too so I don't know what to do.

I've tried powering down and switching on again just now but phone goes straight into "installing system update..." mode.

Has anyone else seen this problem? Really worried me now as it renders my phone completely useless :'(

Any ideas?

Thanks,

Ben