I think Snap unmeter quickflix, and are well regarded on this forum.
Snap are definitely outstanding, I'm with them and I highly recommend them, however I don't think they do zero-rate quickflix (yet?) Must admit I've not tried it myself, but when I last looked into it they had made some noise about zero-rating quickflix but hadn't done it yet and it's been in limbo ever since.
Having said that, if you're with them and buy one of their data add-ons it comes with oodles of data (smallest is 100GB and it's pretty cheap - I have this one) - you get zero-rated data\unlimited downdloads from 1am - 7am. In the couple of months since they added this I've literaly come nowhere even remotely near hitting my data caps - I just schedule backups and large downloads, steam downloads, etc for the 1am-7am window.