Lollipop on HTC One M8

I'm trying to update to Lollipop OTA on my HTC One M8, rooted, S-ON. I've read that it won't work with a custom recovery (I was using CWM) so I flashed a stock recovery and removed SuperSU, and that all seemed well and good but the update still won't apply. It just boots into the recovery menu(?) then stops.

Please help!